cluster: speed scheduler exit

[bufferflies]

What problem does this PR solve?

closed #4146 speed schedule exit

What is changed and how it works?

pause scheduler after accept stop signal, and do not loop

Check List

Tests

• Manual test (add detailed scripts or steps below)

Code changes

Side effects

Related changes

• Need to cherry-pick to the release branch

Release note

speed scheduler exit  

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• nolouch
• rleungx

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[nolouch]

the commit is strange.

[nolouch]

/run-unit-test

[codecov]

Codecov Report

Merging #4148 (6b3b72b) into master (5e0c212) will increase coverage by 0.07%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #4148      +/-   ##
==========================================
+ Coverage   74.70%   74.77%   +0.07%     
==========================================
  Files         260      260              
  Lines       26625    26629       +4     
==========================================
+ Hits        19889    19913      +24     
+ Misses       4950     4937      -13     
+ Partials     1786     1779       -7     

Flag	Coverage Δ
unittests	74.77% <100.00%> (+0.07%)	⬆️

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

Impacted Files	Coverage Δ
server/cluster/cluster.go	82.80% <100.00%> (+0.11%)	⬆️
server/cluster/coordinator.go	74.62% <100.00%> (+0.22%)	⬆️
server/id/id.go	76.19% <0.00%> (-4.77%)	⬇️
server/schedulers/random_merge.go	60.00% <0.00%> (-3.34%)	⬇️
server/schedule/hbstream/heartbeat_streams.go	71.71% <0.00%> (-1.02%)	⬇️
server/server.go	71.40% <0.00%> (-0.45%)	⬇️
server/grpc_service.go	49.74% <0.00%> (-0.11%)	⬇️
server/tso/allocator_manager.go	65.16% <0.00%> (+0.16%)	⬆️
server/tso/tso.go	63.06% <0.00%> (+0.56%)	⬆️
... and 6 more

---

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[nolouch]

PTAL @rleungx

[nolouch]

/merge

[ti-chi-bot]

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

/run-all-tests

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: 6b3b72b

[ti-chi-bot]

In response to a cherrypick label: new pull request created: #4198.

[ti-chi-bot]

In response to a cherrypick label: new pull request created: #4199.

[ti-chi-bot]

In response to a cherrypick label: new pull request created: #4200.

[ti-chi-bot]

In response to a cherrypick label: new pull request created: #4201.