Removed incorrect check for returncode
    
    The server installation in most cases returns response code 0 no matter what
    happens except for really severe errors. In this case when we try to uninstall
    the middle replica of a line topology, it fails, notifies us that we should use
    '--ignore-topology-disconnect', but returns 0
    
    https://fedorahosted.org/freeipa/ticket/6300
    
    Reviewed-By: Martin Basti <mbasti@redhat.com>