修复vendor.json: 添加github.com/go-ini/ini

vendor.json缺少github.com/go-ini/ini包的配置，执行make命令编二进制包的时候有以下报错:

Run gofmt on all source files ...
gofmt -l -s -w ...
==> Checking that build is using go version >= 1.10...
go build -o mymon
common/config.go:20:2: cannot find package "github.com/go-ini/ini" in any of:
    /home/mdh67899/go/src/github.com/open-falcon/mymon/vendor/github.com/go-ini/ini (vendor tree)
    /usr/local/go/src/github.com/go-ini/ini (from $GOROOT)
    /home/mdh67899/go/src/github.com/go-ini/ini (from $GOPATH)
Makefile:43: recipe for target 'build' failed
make: *** [build] Error 1

@UlricQin @MistShi

open-falcon / mymon

修复vendor.json: 添加github.com/go-ini/ini #52