*: use another etcd client for election (#6409)

[ti-chi-bot]

This is an automated cherry-pick of #6409

What problem does this PR solve?

Issue Number: Ref #6403.

What is changed and how does it work?

This PR tries to use another etcd client for the election to prevent the throttling of one connection.

Check List

Tests

• Manual test (TODO)

Release note

None.

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• nolouch

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[codecov]

Codecov Report

Patch coverage: 50.00% and project coverage change: -0.04 ⚠️

Comparison is base (10b691a) 75.67% compared to head (94a0307) 75.64%.

Additional details and impacted files

@@               Coverage Diff               @@
##           release-6.5    #6454      +/-   ##
===============================================
- Coverage        75.67%   75.64%   -0.04%     
===============================================
  Files              330      330              
  Lines            33009    33023      +14     
===============================================
  Hits             24980    24980              
  Misses            5882     5882              
- Partials          2147     2161      +14     

Flag	Coverage Δ
unittests	75.64% <50.00%> (-0.04%)	⬇️

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

Impacted Files	Coverage Δ
server/server.go	74.57% <50.00%> (-1.18%)	⬇️

... and 28 files with indirect coverage changes

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[rleungx]

@nolouch PTAL

[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

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[ti-chi-bot]

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

Commit hash: 94a0307

[ti-chi-bot]

@ti-chi-bot: Your PR was out of date, I have automatically updated it for you.

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