Raise an exception when running EE tests if no license is provided and one is not installed
Problem
It's possible to run EE tests against an instance that doesn't have a license, and we can forget to provide a license to be installed automatically. In that case it's not obvious why the tests fail. This has bitten me a few times when running tests against a fresh omnibus-gitlab instance.
Proposal
Check for an EE license before running EE tests. The QA framework already installs an EE license automatically if provided, but if one isn't provided it runs the tests anyway. We could add a check there, and raise an exception if no license is provided and there isn't one installed.
We could also add a check in gitlab-qa
so that it raises an exception if we try to use an EE release and haven't provided a license. But it shouldn't prevent us from running tests against an existing instance - we can leave that the to QA framework.