koordlet: revise flaky test in pleg

[saintube]

Ⅰ. Describe what this PR does

Ⅱ. Does this pull request fix one issue?

Ⅲ. Describe how to verify it

Ⅳ. Special notes for reviews

V. Checklist

• I have written necessary docs and comments
• I have added necessary unit tests and integration tests
• All checks passed in make test

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 68.55%. Comparing base (f5b611f) to head (eb5888b).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2060      +/-   ##
==========================================
- Coverage   68.58%   68.55%   -0.04%     
==========================================
  Files         430      430              
  Lines       39387    39387              
==========================================
- Hits        27015    27000      -15     
- Misses      10036    10047      +11     
- Partials     2336     2340       +4     

Flag	Coverage Δ
unittests	68.55% <ø> (-0.04%)	⬇️

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[zwzhang0107]

/lgtm
/approve

[koordinator-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: zwzhang0107

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