Let net.Listen pick a port for grpc servers generated in tests

[ecordell]

Description of the change:
Let net.Listen pick the port for test grpc servers. This seems to avoid issues where the ports are not freed in time for subsequent tests.

Motivation for the change:
This maybe fixes #2092, though I was unable to reproduce it locally (prior to the change in this PR, I had trouble running this test at all locally)

Reviewer Checklist

• Implementation matches the proposed design, or proposal is updated to match implementation
• Sufficient unit test coverage
• Sufficient end-to-end test coverage
• Docs updated or added to /doc
• Commit messages sensible and descriptive

[dinhxuanvu]

/lgtm

[openshift-ci]

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[dinhxuanvu]

Interesting. We have the csv-role already exists flake and now it seems with this PR we have csv-rolebinding already exists flake.

[timflannagan]

That should've been fixed in the previous PR - I wonder if we're simply testing out-of-date content on a per-PR basis? Was this PR rebased against the previous one, or was that other flake PR merged in parallel while this one was opened?