[ISSUE-489][Minor] Cleanup some code

[iwangjie]

What changes were proposed in this pull request?

We can simplify and standardize some of the code.

Why are the changes needed?

Fixes #489

Does this PR introduce any user-facing change?

No.

How was this patch tested?

Existing CI.

[kaijchen]

LGTM, thanks @iwangjie for the work.

[codecov-commenter]

Codecov Report

Merging #490 (43c69c9) into master (654d8c7) will decrease coverage by 0.00%.
The diff coverage is 55.55%.

@@             Coverage Diff              @@
##             master     #490      +/-   ##
============================================
- Coverage     58.77%   58.77%   -0.01%     
+ Complexity     1705     1703       -2     
============================================
  Files           206      206              
  Lines         11469    11464       -5     
  Branches       1023     1021       -2     
============================================
- Hits           6741     6738       -3     
+ Misses         4317     4315       -2     
  Partials        411      411              

Impacted Files	Coverage Δ
...pache/hadoop/mapreduce/task/reduce/RssFetcher.java	92.30% <ø> (+1.39%)	⬆️
.../org/apache/uniffle/common/config/ConfigUtils.java	34.44% <0.00%> (ø)
.../java/org/apache/uniffle/server/ShuffleServer.java	64.38% <0.00%> (ø)
.../org/apache/uniffle/server/ShuffleTaskManager.java	76.56% <0.00%> (ø)
...e/uniffle/storage/handler/impl/HdfsFileWriter.java	55.88% <0.00%> (ø)
...g/apache/hadoop/mapred/SortWriteBufferManager.java	79.89% <100.00%> (-0.22%)	⬇️
...ava/org/apache/uniffle/common/util/RetryUtils.java	71.42% <100.00%> (-1.30%)	⬇️
...assignment/PartitionBalanceAssignmentStrategy.java	94.82% <100.00%> (ø)
...e/storage/handler/impl/HdfsShuffleReadHandler.java	56.25% <100.00%> (ø)

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[kaijchen]

Thanks @iwangjie for your contribution.