After in-test self.setUp(), give worker time to start
    
    Normally, nose is still setting things up itself during setUp, so we
    have a few seconds between setUp and the test starting.
    With this one, we don't, and Celery 3 nees the worker to be running
    at least once before the client starts.
    
    Signed-off-by: Patrick Uiterwijk <puiterwijk@redhat.com>