svg render bug on label of markline

[x] I am using English in this issue. 在这个 Issue 中我使用了英文（强烈建议）。

General Questions

the Echarts svg renderer is different on markline label with canvas renderer.

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[x] Required: I have read the document and examples and tried to solve it by myself. （必填）我读过了文档和教程，并且曾试图自己解决问题。
[x] Required: I have searched for similar issues and that didn't help. （必填）我搜索过 issue 但是没有帮助。
[x] Required: I have tried with the latest version of ECharts and still have this problem. （必填）我试过最新版本的 ECharts，还是存在这个问题。

In this issue, I have provided information with: 在这个 issue 中我提供了以下信息：

[x] Required: issue type；（必填）issue 类型
[ ] Required: one sentence description in issue details；（必填）一句话的问题描述
[ ] Required: demo；（必填）能反映问题的例子（如果你想提问或报 bug）
[ ] Required: ECharts version；ECharts 版本

Issue Type

[ ] I have a question to ask about how to use ECharts to ...；我想提问如何使用 ECharts 实现某功能
[x] I have a bug to report；我想要报 bug
[ ] I have a feature to request, e.g.: I'd like a new feature that ...；我需要一个新功能
[ ] I have a feature to enhance, e.g.: The current feature should be improved in the way that ...；我希望改进某个功能
[ ] There's something wrong with the documents；文档有些问题
[ ] Others, or I'm not sure which issue types to choose here；其他，或我不知道应该选什么类型

Issue Details

{DESCRIBE_HERE}

Expected Behavior

Label'backgroundColor on markline is effict.

{DESCRIBE_HERE}

Current Behavior

{DESCRIBE_HERE}

Online Example

THIS IS REQUIRED FOR ALL BUG REPORTS AND QUESTIONS!!! 如果是提问或报 bug 一定要提供这一项！

{ADD_LINK_OF_DEMO_HERE}

var dom = document.getElementById('div')
var myE = echarts.init(dom, null)
var option = {
    "ext_js_list": [],
    "title": {
        "y": "",
        "text": "",
        "textStyle": {
            "fontWeight": 700
        },
        "x": "center",
        "show": false
    },
    "color": ["#8AB6D5", "#A5D9FD", "#B2CBE1", "#A6A6A6", "#D3D3D3", "#7D9BBB", "#78BCF9", "#93819A", "#E5EFF6", "#295378"],
    "series": [{
        "markLine": {
            "data": [{
                "label": {
                    "normal": {
                        "padding": [
                            4,
                            4
                        ],
                        "fontStyle": "normal",
                        "fontSize": 12,
                        "backgroundColor": null,
                        "show": true,
                        "color": null,
                        "position": "middle",
                        // "formatter": this.getNormalFormatterHandler({ttype: 'num', digit: 1, millesimal: false, showText: true, showAxis: false, wrapText: false, isMarkline: true, marklineTitle: '\u5168\u56fd\u603b\u5206'})
                    }
                },
                "lineStyle": {
                    "normal": {
                        "color": "#FD3C3C",
                        "width": "2",
                        "type": "dashed"
                    }
                },
                "name": "",
                "yAxis": 90.55458675373666
            }, {
                "label": {
                    "padding": [
                        4,
                        4
                    ],
                    "fontStyle": "normal",
                    "fontSize": 12,
                    "backgroundColor": "#f66",
                    "show": true,
                    "color": "#000",
                    "position": "start"
                },
                "lineStyle": {
                    "normal": {
                        "color": "#4E6F56",
                        "width": "2",
                        "type": "dashed"
                    }
                },
                "name": "",
                "yAxis": 92.12229838799301
            }],
            "precision": 1,
            "label": {
                "normal": {
                    "fontStyle": "normal",
                    "show": true,
                    "padding": [
                        4,
                        4
                    ],
                    "fontSize": 12,
                    "position": "middle",
                    "formatter": "{a} {b} : {c}"
                }
            }
        },
        "name": "\u603b\u5206",
        "barGap": "10%",
        "itemStyle": {
            "normal": {
                "color": "#7BADD2"
            }
        },
        "barMaxWidth": "100",
        "field_id": "5b8e1d5962e376257b85aa75",
        "tooltip": {
            // "formatter": this.getNormalFormatterHandler({ttype: 'num', digit: 1, millesimal: false, showText: true, showAxis: true, wrapText: false, isMarkline: false, marklineTitle: ''})
        },
        "label": {
            "normal": {
                "position": "insideBottom",
                "align": "center",
                // "formatter": this.getNormalFormatterHandler({ttype: 'num', digit: 1, millesimal: false, showText: false, showAxis: false, wrapText: false, isMarkline: false, marklineTitle: ''}), 
                "textBorderWidth": 2,
                "show": true
            }
        },
        "animation": false,
        "data": [
            95.31360112755463,
            78.7878787878788,
            96.53679653679654,
            89.43360403037822,
            86.13636363636364,
            88.52511125238398,
            93.63636363636364,
            94.8051948051948,
            95.6387047296138,
            91.81818181818183
        ],
        "type": "bar",
        "id": "5b8e1d5962e376257b85aa75"
    }],
    "yAxis": [{
        "nameLocation": "middle",
        "axisTick": {
            "show": false
        },
        "scale": true,
        "name": "",
        "show": true,
        "axisLabel": {
            "textStyle": {
                "color": "#787878",
                "fontSize": 10
            },
            // "formatter": this.getNormalFormatterHandler({ttype: 'num', digit: 1, millesimal: false, showText: false, showAxis: false, wrapText: false, isMarkline: false, marklineTitle: ''}), 
            "show": true
        },
        "splitLine": {
            "lineStyle": {
                "color": "#e9e9e9"
            }
        },
        "nameTextStyle": {
            "color": "#787878",
            "fontSize": 10
        },
        "splitNumber": 5,
        "axisLine": {
            "show": false
        },
        "nameGap": 35,
        "type": "value"
    }],
    "tooltip": {
        "axisPointer": {
            "type": "shadow"
        },
        "trigger": "item",
        "extraCssText": "border-radius: 0px;",
        "textStyle": {
            "fontSize": 12
        }
    },
    "visualMap": [],
    "grid": [{
        "top": 40,
        "right": 20,
        "bottom": 20,
        "containLabel": true,
        "left": 20
    }],
    "xAxis": [{
        "nameLocation": "middle",
        "splitNumber": "10",
        "minInterval": 1,
        "name": "",
        "show": true,
        "data": ["\u9752\u5c9b\u5206\u533a", "\u70df\u5a01\u5206\u533a", "\u8c6b\u5357\u5206\u533a", "\u8c6b\u4e2d\u5206\u533a", "\u4e34\u6c82\u5206\u533a", "\u5408\u80a5\u5206\u533a", "\u7696\u5317\u5206\u533a", "\u8c6b\u5317\u5206\u533a", "\u6d4e\u5357\u5206\u533a", "\u5c71\u897f\u5206\u533a"],
        "axisLabel": {
            "textStyle": {
                "color": "#787878",
                "fontSize": 10
            },
            "inside": false,
            "rotate": 0,
            "show": true
        },
        "boundaryGap": ["10%", "10%"],
        "nameTextStyle": {
            "color": "#787878",
            "fontSize": 10
        },
        "nameGap": 35,
        "axisLine": {
            "lineStyle": {
                "color": "#A6A6A6"
            },
            "show": true
        },
        "triggerEvent": true,
        "z": 10,
        "type": "category",
        "axisTick": {
            "show": false
        }
    }],
    "dataZoom": [{
        "end": 100,
        "bottom": "0%",
        "show": false,
        "xAxisIndex": [
            0
        ],
        "start": 0,
        "type": "slider"
    }],
    "toolbox": {
        "feature": {
            "restore": {
                "show": true
            },
            "saveAsImage": {
                "show": true
            },
            "dataView": {
                "readOnly": false,
                "show": true
            },
            "mark": {
                "show": true
            },
            "myDownloadData": {
                "title": "\u4e0b\u8f7d\u6570\u636e",
                "icon": "image://http://echarts.baidu.com/images/favicon.png",
                "onclick": self.downloadData,
                "show": true
            },
            "myShowOption": {
                "title": "\u7f16\u8f91",
                "icon": "image://http://echarts.baidu.com/images/favicon.png",
                "onclick": self.showOption,
                "show": true
            },
            "myGoBack": {
                "title": "\u8fd4\u56de",
                "icon": "image://http://echarts.baidu.com/images/favicon.png",
                "onclick": self.goBack,
                "show": false
            }
        },
        "show": false
    },
    "legend": {
        "textStyle": {
            "padding": 0,
            "lineHeight": 10,
            "fontSize": 10
        },
        "show": false,
        "itemHeight": 12,
        "itemGap": 5,
        "padding": 0,
        "itemWidth": 12,
        "pageTextStyle": {},
        "data": [{
            "name": "\u603b\u5206",
            "icon": "circle"
        }],
        "left": "center"
    }
}
myE.setOption(option)

Topics

[ ] Legend
[ ] Tooltip
[ ] Event
[ ] Performance
[x] SVG
[ ] Map
[ ] ECharts GL
[ ] Third-party libraries, e.g.: Vue.js, React

Anything Else We Need to Know

svg renderer

canvas renderer

canvas renderer exist backgroundColor on markline' label, but svg renderer is not.

{DESCRIBE_HERE}

Environment

ECharts version；ECharts 版本: echarts version 4.2.0-rc.1
[ ] It happens only on certain browsers or operating systems. 对于特定浏览器或操作系统才会出现的问题，请提供相应环境信息：{BROWSER_VERSION_OR_OS_INFORMATION_HERE}

apache / echarts