Fix notification timing issue by sending in the latter of 2 events (#12110)

* Track host_status_counts and use that to process notifications

* Remove now unused setting

* Back out changes to callback class not needed after all

* Skirt the need for duck typing by leaning on the cached field

* Delete tests for deleted task

* Revert "Back out changes to callback class not needed after all"

This reverts commit 3b8ae350d218991d42bffd65ce4baac6f41926b2.

* Directly hardcode stats_event_type for callback class

* Fire notifications if stats event was never sent

* Remove test content for deleted methods

* Add placeholder for when no hosts matched

* Make field default be None, denote events processed with empty dict

* Make UI process null value for host_status_counts

* Fix tracking of EOF dispatch for system jobs

* Reorganize EVENT_MAP into class properties

* Consolidate conditional I missed from EVENT_MAP refactor

* Give up on the null condition, also applies for empty hosts

* Remove cls position argument not being used

* Move wrapup method out of class, add tests

awx/settings/defaults.py

@@ -997,9 +997,6 @@ BROADCAST_WEBSOCKET_NEW_INSTANCE_POLL_RATE_SECONDS = 10
 # How often websocket process will generate stats
 BROADCAST_WEBSOCKET_STATS_POLL_RATE_SECONDS = 5
 
-# Number of times to retry sending a notification when waiting on a job to finish.
-AWX_NOTIFICATION_JOB_FINISH_MAX_RETRY = 5
-
 DJANGO_GUID = {'GUID_HEADER_NAME': 'X-API-Request-Id'}
 
 # Name of the default task queue