[simulator] Fix transport_url usage
[simulator] Fix transport_url usage

1) Remove hardcoding 'redis' matchmaker from any zmq:// transport because it's
   fails in cases zmq+etcd:// or zmq+sentinel:// urls.
2) Allow to use transport_url from config file by removing default value for
   args.url option. In this case by default args.url is None and
   transport_url will be used from config file.

Change-Id: I1edcabe46b1e92dd4e6eccc9151b50d03f394186

ozamiatin/oslo.messaging,ozamiatin/oslo.messaging