Support RHEL9 and Rocky9: fix missing changes

[hanwen-pcluste]

This PR fixes minor bugs from #6018

1. Add Rocky9 and RHEL9 to the kernel pinning logic. This was missed because the kernel pinning logic is new.
2. Only test one NOT_RELEASED_OSES to keep the number of tests from increasing

Checklist

• Make sure you are pointing to the right branch.
• If you're creating a patch for a branch other than develop add the branch name as prefix in the PR title (e.g. [release-3.6]).
• Check all commits' messages are clear, describing what and why vs how.
• Make sure to have added unit tests or integration tests to cover the new/modified code.
• Check if documentation is impacted by this change.

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (aa66103) 90.21% compared to head (9ea1de8) 90.21%.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #6103   +/-   ##
========================================
  Coverage    90.21%   90.21%           
========================================
  Files          181      181           
  Lines        15837    15837           
========================================
  Hits         14287    14287           
  Misses        1550     1550           

Flag	Coverage Δ
unittests	90.21% <100.00%> (ø)

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