Eliminate redundant Pod Get.

[mattmoor]

The TaskRun reconciler was doing a Pod Get immediately prior to calling StopSidecars, which immediate refetches the Pod. This adapts StopSidecars to take the namespace/name and return the resulting Pod to elide the redundant fetch, and avoids wrapping errors in the case of NotFound, so that callers can be sensitive to that.

See also this slack thread: https://tektoncd.slack.com/archives/CLCCEBUMU/p1604503658269500

/kind bug

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/assign @imjasonh @vdemeester @afrittoli

[mattmoor]

/test check-pr-has-kind-label

[tekton-robot]

The following is the coverage report on the affected files.
Say /test pull-tekton-pipeline-go-coverage to re-run this coverage report

File	Old Coverage	New Coverage	Delta
pkg/pod/entrypoint.go	85.1%	84.1%	-1.0

[imjasonh]

/lgtm

Does this look less flaky if you run e2e cancel/timeout tests many times?

[vdemeester]

/meow

[tekton-robot]

@vdemeester:

In response to this:

/meow

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[mattmoor]

/retest

Does this look less flaky if you run e2e cancel/timeout tests many times?

My testing is via automation that doesn't lend itself to trying that easily, but while this works its way in, I can stage a PR that pulls it in and retest it until GHA throttles me to death 😉

[mattmoor]

1/3 downstream legs have passed 🤞