[ios]Fixed the problem that the list was not automatically restored when the loading tag was pulled up under certain conditions

[yuditxj]

Fix the problem that when the list is under one piece of data, the loading label will be displayed by default in the drop-down refresh list

复现条件: list标签数据不超过一屏时，同时存在refresh和loading标签，若上拉加载列表(没有更多数据)，仅仅快速切换(100ms)loading标签的display属性由true为false，发现列表位置不会自动还原

原因: Probably setContentOffset: has higher priority than setContentOffset:animated:

方案: 参考refresh标签的说明，针对displayState字段不同值，调整设置setContentOffset方式

Brief Description of the PR

Checklist

• Demo:http://dotwe.org/vue/ab6efd1b38c9beaec2cae3a99e3ecf79

• Documentation:

[Txink]

麻烦合并一下PR，还有就是能提供一个验证demo么

[yuditxj]

麻烦合并一下PR，还有就是能提供一个验证demo么 demo地址： http://dotwe.org/vue/ab6efd1b38c9beaec2cae3a99e3ecf79