Add a specific tag for tests where the fix is not implemented yet

[martinobanana]

Before we have the complete solution in #1182 , we need a quick workaround to mark tests which needs to be skipped due to the fix in rpm not implemented yet.

From top of my mind, it could be @not_implemented or something similar. In case scenario is marked with this tag, the scenario would be skipped.

Having the tag will enable us to backport tests to rhel* branches as soon as possible. The PR review for some tests takes some time and could block the release of the fix. Reviewing the PR early avoids that. The only thing to do later is to remove the tag via simple PR just before the build is available.