Ticket 47827 - online import crashes server if using verbose error logging
    
    Bug Description:  When using verbose logging and running an import task, the
                      server will crash at the end of the import.  The verbose
                      logging changes the internal timing and exposes a race condition
                      where the task queue frees the import job before the import
                      finishes.
    
    Fix Description:  Wait for the backend instance to be set as "not busy" before
                      freeing the import task.
    
    https://fedorahosted.org/389/ticket/47827
    
    Reviewed by: nhosoi(Thanks!)