scheduler: fix fairness ut

[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

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 68.62%. Comparing base (f436876) to head (4b5ed7c).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2069      +/-   ##
==========================================
- Coverage   68.63%   68.62%   -0.02%     
==========================================
  Files         430      430              
  Lines       39534    39534              
==========================================
- Hits        27136    27131       -5     
- Misses      10056    10060       +4     
- Partials     2342     2343       +1     

Flag	Coverage Δ
unittests	68.62% <ø> (-0.02%)	⬇️

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

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[saintube]

/lgtm

[koordinator-bot]

[APPROVALNOTIFIER] This PR is APPROVED

Approval requirements bypassed by manually added approval.

This pull-request has been approved by:

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files:

• pkg/scheduler/OWNERS

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment