*: make TestTSOKeyspaceGroupSplitElection stable

[rleungx]

What problem does this PR solve?

Issue Number: Close #8099

What is changed and how does it work?

The groupSplitPatroller may run immediately after the split request is finished. Then the check may fail since the split is finished.

Check List

Tests

• Unit test

Release note

None.

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• lhy1024

To complete the pull request process, please ask the reviewers in the list to review by filling /cc @reviewer in the comment.
After your PR has acquired the required number of LGTMs, you can assign this pull request to the committer in the list by filling /assign @committer in the comment to help you merge this pull request.

The full list of commands accepted by this bot can be found here.

Reviewer can indicate their review by submitting an approval review.
Reviewer can cancel approval by submitting a request changes review.

[codecov]

Codecov Report

Merging #8110 (9a188d1) into master (882d2e5) will increase coverage by 0.02%.
Report is 3 commits behind head on master.
The diff coverage is 100.00%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #8110      +/-   ##
==========================================
+ Coverage   77.28%   77.30%   +0.02%     
==========================================
  Files         470      470              
  Lines       61129    61143      +14     
==========================================
+ Hits        47244    47269      +25     
+ Misses      10310    10306       -4     
+ Partials     3575     3568       -7     

Flag	Coverage Δ
unittests	77.30% <100.00%> (+0.02%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

[rleungx]

/merge

[ti-chi-bot]

@rleungx: It seems you want to merge this PR, I will help you trigger all the tests:

/run-all-tests

You only need to trigger /merge once, and if the CI test fails, you just re-trigger the test that failed and the bot will merge the PR for you after the CI passes.

If you have any questions about the PR merge process, please refer to pr process.

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the ti-community-infra/tichi repository.

[ti-chi-bot]

This pull request has been accepted and is ready to merge.

Commit hash: 9a188d1