refactor start_event_queryset into model

awx/api/views.py

@@ -2967,21 +2967,7 @@ class JobJobTasksList(BaseJobEventsList):
             return ({'detail': 'Parent event not found.'}, -1, status.HTTP_404_NOT_FOUND)
         parent_task = parent_task[0]
 
-        # Some events correspond to a playbook or task starting up,
-        # and these are what we're interested in here.
-        STARTING_EVENTS = ('playbook_on_task_start', 'playbook_on_setup')
-
-        # We need to pull information about each start event.
-        #
-        # This is super tricky, because this table has a one-to-many
-        # relationship with itself (parent-child), and we're getting
-        # information for an arbitrary number of children. This means we
-        # need stats on grandchildren, sorted by child.
-        queryset = (JobEvent.objects.filter(parent__parent=parent_task,
-                                            parent__event__in=STARTING_EVENTS)
-                                    .values('parent__id', 'event', 'changed')
-                                    .annotate(num=Count('event'))
-                                    .order_by('parent__id'))
+        queryset = JobEvent.start_event_queryset(parent_task)
 
         # The data above will come back in a list, but we are going to
         # want to access it based on the parent id, so map it into a