etcdutil_test: close goroutine leak when block in accept

[HuSharp]

What problem does this PR solve?

Issue Number: Ref #7782, tested by #7777

What is changed and how does it work?

etcdutil_test: close goroutine leak when block in accept

Check List

Tests

• Unit test
• Integration test

Release note

None.

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• JmPotato
• rleungx

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[codecov]

Codecov Report

Merging #7787 (ee95d1d) into master (cce1464) will decrease coverage by 0.06%.
The diff coverage is n/a.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #7787      +/-   ##
==========================================
- Coverage   73.45%   73.40%   -0.06%     
==========================================
  Files         432      432              
  Lines       47843    47843              
==========================================
- Hits        35145    35118      -27     
- Misses       9654     9681      +27     
  Partials     3044     3044              

Flag	Coverage Δ
unittests	73.40% <ø> (-0.06%)	⬇️

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[JmPotato]

/merge

[ti-chi-bot]

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[ti-chi-bot]

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

Commit hash: 018ede7