replace celery task decorators with a kombu-based publisher

this commit implements the bulk of `awx-manage run_dispatcher`, a new
command that binds to RabbitMQ via kombu and balances messages across
a pool of workers that are similar to celeryd workers in spirit.
Specifically, this includes:

- a new decorator, `awx.main.dispatch.task`, which can be used to
  decorate functions or classes so that they can be designated as
  "Tasks"
- support for fanout/broadcast tasks (at this point in time, only
  `conf.Setting` memcached flushes use this functionality)
- support for job reaping
- support for success/failure hooks for job runs (i.e.,
  `handle_work_success` and `handle_work_error`)
- support for auto scaling worker pool that scale processes up and down
  on demand
- minimal support for RPC, such as status checks and pool recycle/reload

awx/main/tests/unit/test_tasks.py

@@ -67,7 +67,7 @@ def test_work_success_callback_missing_job():
     task_data = {'type': 'project_update', 'id': 9999}
     with mock.patch('django.db.models.query.QuerySet.get') as get_mock:
         get_mock.side_effect = ProjectUpdate.DoesNotExist()
-        assert tasks.handle_work_success(None, task_data) is None
+        assert tasks.handle_work_success(task_data) is None
 
 
 def test_send_notifications_list(mocker):