scheduler: fix scatter range scheduler limit (#3361)

[ti-srebot]

cherry-pick #3361 to release-5.0-rc
You can switch your code base to this Pull Request by using git-extras:

# In pd repo:
git pr https://github.com/tikv/pd/pull/3402

After apply modifications, you can push your change to this PR via:

git push [email protected]:ti-srebot/pd.git pr/3402:release-5.0-rc-680a3a48d3cd

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What problem does this PR solve?

Closes #3356

What is changed and how it works?

This PR fixes the limit constriction for scatter range scheduler.

Check List

Tests

• Unit test

Related changes

• Need to cherry-pick to the release branch

Release note

• Fix the limit constriction of the scatter range scheduler

[ti-chi-bot]

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[ti-srebot]

@rleungx you're already a collaborator in bot's repo.

[codecov]

Codecov Report

Merging #3402 (4553dd5) into release-5.0-rc (f4e7924) will decrease coverage by 0.00%.
The diff coverage is 100.00%.

@@                Coverage Diff                 @@
##           release-5.0-rc    #3402      +/-   ##
==================================================
- Coverage           74.12%   74.11%   -0.01%     
==================================================
  Files                 243      243              
  Lines               23088    23093       +5     
==================================================
+ Hits                17113    17116       +3     
  Misses               4401     4401              
- Partials             1574     1576       +2     

Flag	Coverage Δ
unittests	74.11% <100.00%> (-0.01%)	⬇️

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

Impacted Files	Coverage Δ
server/schedulers/scatter_range.go	81.37% <100.00%> (+0.66%)	⬆️
server/election/lease.go	89.83% <0.00%> (-3.39%)	⬇️
server/encryptionkm/key_manager.go	71.78% <0.00%> (-1.66%)	⬇️
server/election/leadership.go	80.48% <0.00%> (-1.22%)	⬇️
server/tso/allocator_manager.go	75.00% <0.00%> (-0.81%)	⬇️
server/grpc_service.go	55.99% <0.00%> (-0.69%)	⬇️
server/tso/tso.go	78.61% <0.00%> (-0.63%)	⬇️
server/member/member.go	67.93% <0.00%> (-0.55%)	⬇️
server/server.go	73.25% <0.00%> (-0.48%)	⬇️
server/cluster/cluster.go	80.88% <0.00%> (+0.50%)	⬆️
... and 6 more

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[Yisaer]

/merge

[ti-chi-bot]

@Yisaer: 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: 4553dd5

[rleungx]

/run-all-tests