tests/etcd: remove mod to make test stable

[HuSharp]

What problem does this PR solve?

Issue Number: Close #8091, Ref #7969

What is changed and how does it work?

Because we create many etcd cluster concurrently when using pd-ut which makes etcd test unstable

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)

Release note

None.

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• nolouch

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[codecov]

Codecov Report

Merging #8102 (ffb9320) into master (882d2e5) will increase coverage by 0.06%.
Report is 1 commits behind head on master.
The diff coverage is 100.00%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #8102      +/-   ##
==========================================
+ Coverage   77.28%   77.35%   +0.06%     
==========================================
  Files         470      470              
  Lines       61129    61129              
==========================================
+ Hits        47244    47285      +41     
+ Misses      10310    10289      -21     
+ Partials     3575     3555      -20     

Flag	Coverage Δ
unittests	77.35% <100.00%> (+0.06%)	⬆️

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[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: ffb9320