Improve the actor check for running internal TF

[lbarcziova]

Since for test jobs, builds may be required, we additionally don't allow builds if there is an internal TF test job with the same trigger configured (builds could trigger the test job that was not allowed). The reason for doing this is that we don't store the actor anywhere and therefore cannot run the check directly when running tests if there was a required build before. A solution to this would be to store the actor in the DB. This way we could run the actor check directly when running the test job.

TODO:

• [ ] store the actor from the webhook in the DB
• [ ] remove this check class for CoprBuildHandler
• [ ] for TestingFarmHandler remove this condition

[lachmanfrantisek]

This is still an issue and confusing for people.