This PR removed `unittest.MainTest` the second parameter
`TestOptions.GiteaRoot`. Now it detects the root directory by current
working directory.
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Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>
The admin config page has been broken for many many times, a little
refactoring would make this page panic.
So, add a test for it, and add another test to cover the 500 error page.
Co-authored-by: Giteabot <teabot@gitea.io>