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/main/models/notifications.py

@@ -421,21 +421,8 @@ class JobNotificationMixin(object):
         The context will contain allowed content retrieved from a serialized job object
         (see JobNotificationMixin.JOB_FIELDS_ALLOWED_LIST the job's friendly name,
         and a url to the job run."""
-        job_context = {'host_status_counts': {}}
-        summary = None
-        try:
-            has_event_property = any([f for f in self.event_class._meta.fields if f.name == 'event'])
-        except NotImplementedError:
-            has_event_property = False
-        if has_event_property:
-            qs = self.get_event_queryset()
-            if qs:
-                event = qs.only('event_data').filter(event='playbook_on_stats').first()
-                if event:
-                    summary = event.get_host_status_counts()
-        job_context['host_status_counts'] = summary
         context = {
-            'job': job_context,
+            'job': {'host_status_counts': self.host_status_counts},
             'job_friendly_name': self.get_notification_friendly_name(),
             'url': self.get_ui_url(),
             'job_metadata': json.dumps(self.notification_data(), ensure_ascii=False, indent=4),