* fix Group.RotateFile need call Flush() before rename. #2428
* fix some review issue. #2428
refactor Group's config: replace setting member with initial option
* fix a handwriting mistake
* fix a time window error between rename and write.
* fix a syntax mistake.
* change option name Get_ to With_
* fix review issue
* fix review issue
1) no need to stop the ticker in createTestGroup() method
2) now there is a symmetry - we start the ticker in OnStart(), we stop it
in OnStop()
Refs #2072
Previously we logged `Testing for i <i>` for all i in [0,100).
This was unnecessary. This changes it to just log the value for i on
error messages, to reduce the unnecessary verbosity in log files.