Shell executor logs through testing.T in upgrade tests

[mgencur]

Similar to knative/serving#14495

Fixes #

Proposed Changes

• Print logs from shell executor to testing.T so that the logs can be found within test scope

Release Note

[knative-prow]

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[knative-prow]

@mgencur: 0 warnings.

In response to this:

Similar to knative/serving#14495

Fixes #

Proposed Changes

• Print logs from shell executor to testing.T so that the logs can be found within test scope

Release Note

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[knative-prow-robot]

PR needs rebase.

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[matzew]

@mgencur can you rebase?

[github-actions]

This Pull Request is stale because it has been open for 90 days with
no activity. It will automatically close after 30 more days of
inactivity. Reopen with /reopen. Mark as fresh by adding the
comment /remove-lifecycle stale.

[houshengbo]

Let me ping @mgencur one more time to see if he can rebase and fix the CI issues with this PR.