[MINOR][IMPROVEMENT][SERVER] Fix server module code style

[jerqi]

What changes were proposed in this pull request?

Solve issue https://github.com/apache/incubator-uniffle/issues/123, solve server module code style problems

Why are the changes needed?

Improve our test code style

Does this PR introduce any user-facing change?

No

How was this patch tested?

I add the test code style check commits, server module passed. https://github.com/jerqi/incubator-uniffle/runs/7691428965?check_suite_focus=true