Use PodResources mount as a path instead of file

[gjulianm]

What does this PR do?

This PR fixes the PodResources socket mount introduced in #1650. By using a file mount directly, if kubelet restarts and recreates the socket, the container will not see the new socket and will keep the reference to the old one, thus losing the connection.

Motivation

Fix a bug with kubelet restarts.

Additional Notes

Minimum Agent Versions

No changes w.r.t #1650

• Agent: v7.62
• Cluster Agent: vX.Y.Z

Describe your test plan

Unit tests should reflect the new change in mounts.

Checklist

• PR has at least one valid label: bug, enhancement, refactoring, documentation, tooling, and/or dependencies
• PR has a milestone or the qa/skip-qa label

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 49.49%. Comparing base (91095b8) to head (c277a79).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1674   +/-   ##
=======================================
  Coverage   49.49%   49.49%           
=======================================
  Files         218      218           
  Lines       21244    21244           
=======================================
  Hits        10515    10515           
  Misses      10182    10182           
  Partials      547      547           

Flag	Coverage Δ
unittests	49.49% <100.00%> (ø)

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

Files with missing lines	Coverage Δ
...ller/datadogagent/defaults/datadogagent_default.go	91.45% <100.00%> (ø)
...nternal/controller/datadogagent/override/global.go	56.52% <100.00%> (ø)
pkg/testutils/builder.go	91.67% <100.00%> (ø)

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[tbavelier]

Not a blocker: could we also envision a test to check a custom provided path (e.g. spec.global.podResourcesSocketPath= /foo/bar) ?

[tbavelier]

Suggested change

	podResourcesVol, podResourcesMount := volume.GetVolumes(v2alpha1.KubeletPodResourcesVolumeName, config.Kubelet.PodResourcesSocketDir, config.Kubelet.PodResourcesSocketDir, false)
	podResourcesVol, podResourcesMount := volume.GetVolumes(v2alpha1.KubeletPodResourcesVolumeName, config.Kubelet.PodResourcesSocketDir, config.Kubelet.PodResourcesSocketDir, true)

Could we use readOnly: true on this volume or that prevents from communicating with the socket ?

[gjulianm]

In my testing it prevented communication, yes.