Validate agent token for duplicate IP addresses

[sjberman]

Problem: In some environments, Pods could share an IP address (for example when a Job completes and a new Pod grabs that IP). This would cause problems when the nginx data plane Pod would attempt to connect to the control plane. The control plane would try to validate the token provided by the nginx agent, by using the IP address in the request to lookup the associated Pod. If multiple Pods existed with that IP address, the control plane would error out.

Solution: Fix the control plane logic to use more criteria when getting the proper Pod to verify the provided token.

Closes #3657

Checklist

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• I have read the CONTRIBUTING doc
• I have added tests that prove my fix is effective or that my feature works
• I have checked that all unit tests pass after adding my changes
• I have updated necessary documentation
• I have rebased my branch onto main
• I will ensure my PR is targeting the main branch and pulling from my branch from my own fork

Release notes

If this PR introduces a change that affects users and needs to be mentioned in the release notes,
please add a brief note that summarizes the change.

Fix an issue where nginx Pod couldn't connect to control plane if multiple Pods shared the nginx Pod's IP address.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 87.12%. Comparing base (c94688c) to head (a987d89).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3673      +/-   ##
==========================================
+ Coverage   87.07%   87.12%   +0.04%     
==========================================
  Files         128      128              
  Lines       15788    15779       -9     
  Branches       62       62              
==========================================
  Hits        13747    13747              
+ Misses       1878     1871       -7     
+ Partials      163      161       -2     

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[bjee19]

@sjberman were you able to get in a situation like in the original issue and manually verify it works?

[sjberman]

@bjee19 Not quite, but I confirmed with the user what causes it, and the code avoids that scenario.

[bjee19]

lgtm, nice