remove support for multi-reader dispatch queue

* Under the new postgres backed notify/listen message queue, this never
actually worked. Without using the database to store state, we can not
provide a at-most-once delivery mechanism w/ multi-readers.
* With this change, work is done ONLY on the node that requested for the
work to be done. Under rabbitmq, the node that was first to get the
message off the queue would do the work; presumably the least busy node.

awx/main/dispatch/publish.py

@@ -8,7 +8,7 @@ from uuid import uuid4
 from django.conf import settings
 from django.db import connection
 
-from . import pg_bus_conn
+from . import pg_bus_conn, get_local_queuename
 
 logger = logging.getLogger('awx.main.dispatch')
 
@@ -73,9 +73,12 @@ class task:
                 kwargs = kwargs or {}
                 queue = (
                     queue or
-                    getattr(cls.queue, 'im_func', cls.queue) or
-                    settings.CELERY_DEFAULT_QUEUE
+                    getattr(cls.queue, 'im_func', cls.queue)
                 )
+                if not queue:
+                    msg = f'{cls.name}: Queue value required and may not me None'
+                    logger.error(msg)
+                    raise ValueError(msg)
                 obj = {
                     'uuid': task_id,
                     'args': args,