*: make TestScheduler stable

[rleungx]

What problem does this PR solve?

Issue Number: Close #6359.

What is changed and how does it work?

When the scheduler is running, if we change pause the scheduler, it might have a time window that the pause status is not set to the diagnostic result which causes the test unstable.

Check List

Tests

• Unit test

Release note

None.

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• CabinfeverB
• JmPotato

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[codecov]

Codecov Report

Patch coverage has no change and project coverage change: -0.06 ⚠️

Comparison is base (4f87e9d) 75.07% compared to head (e3f8525) 75.01%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #6377      +/-   ##
==========================================
- Coverage   75.07%   75.01%   -0.06%     
==========================================
  Files         408      408              
  Lines       40704    40704              
==========================================
- Hits        30559    30535      -24     
- Misses       7496     7520      +24     
  Partials     2649     2649              

Flag	Coverage Δ
unittests	75.01% <ø> (-0.06%)	⬇️

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see 30 files with indirect coverage changes

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[JmPotato]

/merge

[ti-chi-bot]

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

/run-all-tests

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[ti-chi-bot]

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

Commit hash: e3f8525