Re-trigger Copr builds if they were already deleted

[csomh]

Normally when using /packit test, Copr builds are not triggered, if they were previously reported as successful. This information though ("previously reported as successful") can go stale when builds are removed by Copr. This will cause the TF run to fail in the installation step.

Packit should call Copr and explicitly check if the builds are still available before running the tests. If they are missing, /packit test should behave as /packit build.

The above logic should probably be also applied when (re-)triggering tests from the GitHub Checks page.