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/utils/test_reload.py

@@ -8,8 +8,8 @@ def test_produce_supervisor_command(mocker):
     mock_process.communicate = communicate_mock
     Popen_mock = mocker.MagicMock(return_value=mock_process)
     with mocker.patch.object(reload.subprocess, 'Popen', Popen_mock):
-        reload._supervisor_service_command(['beat', 'callback', 'fact'], "restart")
+        reload._supervisor_service_command("restart")
         reload.subprocess.Popen.assert_called_once_with(
-            ['supervisorctl', 'restart', 'tower-processes:receiver',],
+            ['supervisorctl', 'restart', 'tower-processes:*',],
             stderr=-1, stdin=-1, stdout=-1)