Improve our test code style

[jerqi]

Now, there are many style errors in our test code. Because our checkstyle plugin don't check test code. To enable the plugin, we should fix the style errors of the code first. https://github.com/Tencent/Firestorm/pull/155 pr tells us how enable plugin to check test code style. We should enable the plugin to check test code style in one branch, fix the style errors module by module and cherry-pick the fix code in another branch, and raise a fix pr.

This issue will track the pull requests. Related prs: #99 fix common module #122 fix coordinator module #131 fix storage module