Use patch instead of update to replace sidecars with nop image

[prad9192]

What

Changed StopSidecars() to use Patch() instead of Update() when stopping sidecar containers by replacing their images with the nop image.

Why

The original implementation used Update(), which requires an exact resourceVersion match. This causes 409 conflicts when the kubelet updates the pod status between our GET and UPDATE calls (which happens frequently as containers terminate).

This causes the below errors on the pod.

error stopping sidecars of Pod: Operation cannot be fulfilled on pods "...": 
the object has been modified; please apply your changes to the latest version

And the task runs fail with TaskRunResolutionFailed

Even though the task succeeded and sidecars eventually stop, the TaskRun gets marked as failed due to this race condition.
The fix uses JSON Patch (same pattern as UpdateReady() and CancelPod() in this file), which only patches the specific container image fields

Release Notes

Does this PR introduce a user-facing change?

Fixed race condition causing TaskRuns to fail with 409 conflict error when stopping sidecars. 
StopSidecars now uses Patch instead of Update to avoid conflicts with concurrent kubelet pod status updates.

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• ✅ login: prad9192 / name: Pradeep Ashwathanarayan (434ad9a)

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[prad9192]

/retest