[BUG][FOLLOWUP] Fix flaky test of AQESkewedJoinWithLocalOrderTest

[zuston]

What changes were proposed in this pull request?

Fix flaky test of AQESkewedJoinWithLocalOrderTest

Why are the changes needed?

1. The sparksession is not closed by GetReaderTest.java

Does this PR introduce any user-facing change?

No

How was this patch tested?

[codecov-commenter]

Codecov Report

Merging #355 (b3232ae) into master (72ef4e3) will increase coverage by 4.45%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##             master     #355      +/-   ##
============================================
+ Coverage     58.42%   62.88%   +4.45%     
+ Complexity     1554     1426     -128     
============================================
  Files           193      174      -19     
  Lines         10758     8330    -2428     
  Branches        935      814     -121     
============================================
- Hits           6285     5238    -1047     
+ Misses         4102     2812    -1290     
+ Partials        371      280      -91     

Impacted Files	Coverage Δ
.../hadoop/mapreduce/task/reduce/RssEventFetcher.java
.../java/org/apache/hadoop/mapreduce/RssMRConfig.java
...apache/hadoop/mapreduce/v2/app/RssMRAppMaster.java
...preduce/task/reduce/RssRemoteMergeManagerImpl.java
deploy/kubernetes/operator/pkg/webhook/manager.go
...mapreduce/task/reduce/RssInMemoryRemoteMerger.java
...pache/hadoop/mapreduce/task/reduce/RssShuffle.java
...java/org/apache/hadoop/mapred/SortWriteBuffer.java
...y/kubernetes/operator/pkg/webhook/inspector/rss.go
...n/java/org/apache/hadoop/mapreduce/RssMRUtils.java
... and 10 more

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[jerqi]

Kerberos flaky test. Old problem.

[jerqi]

LGTM, thanks @zuston