kola/tests: add openshift tag to OCP tests

[jlebon]

This is part of openshift/os#1445.

Those tests are all actually testing OCP components. In the new model,
they should be run against an OCP layered image instead. Add a tag on
them so that we'll be able to run them separately.

[openshift-ci]

Skipping CI for Draft Pull Request.
If you want CI signal for your change, please convert it to an actual PR.
You can still manually trigger a test run with /test all

[jlebon]

Before doing this, we need to tweak things so that those tests keep running in the !layered streams. (A "layered stream" here refers to a stream built using the approach in openshift/os#1445).

Edit: I've changed the approach here to be more incremental: we still add an openshift tag, but it's no longer a RequiredTag, so should have no effect on current streams.

[jlebon]

/retest

[jlebon]

This is now ready for review!

[yasminvalim]

LGTM!

One question, out of curiosity: Will it become a required tag in the future?

[jlebon]

LGTM!

One question, out of curiosity: Will it become a required tag in the future?

Thanks for reviewing! Yes, probably. Once we've fully switched over to the new stream, then it becomes easier in the pipelines to use required tags so that the kola run on the base compose doesn't have to do --tag !openshift anymore.