pkg/util: use random port to make test TestVerifyCommonNameAndRotate stable (#50369)

[ti-chi-bot]

This is an automated cherry-pick of #50369

What problem does this PR solve?

Issue Number: close #37819

Problem Summary:

What changed and how does it work?

I suspect the unstable is caused by the environment, maybe there are some other service running using that port.
So I change the port to a random one to avoid conflict.

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• No need to test

  • I checked and no code files have been changed.

Side effects

• Performance regression: Consumes more CPU
• Performance regression: Consumes more Memory
• Breaking backward compatibility

Documentation

• Affects user behaviors
• Contains syntax changes
• Contains variable changes
• Contains experimental features
• Changes MySQL compatibility

Release note

Please refer to Release Notes Language Style Guide to write a quality release note.

None

[ti-chi-bot]

This cherry pick PR is for a release branch and has not yet been approved by triage owners.
Adding the do-not-merge/cherry-pick-not-approved label.

To merge this cherry pick:

1. It must be approved by the approvers firstly.
2. AFTER it has been approved by approvers, please wait for the cherry-pick merging approval from triage owners.

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[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (release-7.1@1b13108). Click here to learn what that means.
The diff coverage is n/a.

Additional details and impacted files

@@               Coverage Diff                @@
##             release-7.1     #50374   +/-   ##
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  Coverage               ?   73.5568%           
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  Files                  ?       1207           
  Lines                  ?     379433           
  Branches               ?          0           
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  Hits                   ?     279099           
  Misses                 ?      82605           
  Partials               ?      17729           

[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2024-01-14 04:12:19.927306567 +0000 UTC m=+69981.491604271: ☑️ agreed by AilinKid.

[ti-chi-bot]

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