scheduler: fix UT Fail cause map iterate

[ZiMengSheng]

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

[saintube]

/lgtm

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 66.03%. Comparing base (0b71d81) to head (70d4765).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2311      +/-   ##
==========================================
+ Coverage   66.02%   66.03%   +0.01%     
==========================================
  Files         458      458              
  Lines       53922    53923       +1     
==========================================
+ Hits        35602    35609       +7     
+ Misses      15762    15756       -6     
  Partials     2558     2558              

Flag	Coverage Δ
unittests	66.03% <100.00%> (+0.01%)	⬆️

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