check-compose consumer: run on openqa fedmsgs
    
    this should let the check-compose consumer work on openQA
    fedmsgs, which simplifies it considerably and avoids the need
    to spawn a long-running check-compose process that waits for
    the tests to complete the ugly, old-fashioned way. Instead we
    just run when we see a 'job.done' message with a 'remaining'
    count of 0, meaning it was the last test for the compose and
    all tests for the compose are now complete.
    
    This also supports specifying compose by ID rather than URL,
    as we don't really have the compose URL to emit from openQA.
    
    We could probably clean up check-compose's wait support at
    this point, but I'll leave that for later.