short-circuit event_processing_finished for wf jobs

* wf jobs are a wrapper for other jobs
* they do not process their own job events

awx/main/models/workflow.py

@@ -258,6 +258,10 @@ class WorkflowJobNode(WorkflowNodeBase):
             models.Index(fields=['identifier']),
         ]
 
+    @property
+    def event_processing_finished(self):
+        return True
+
     def get_absolute_url(self, request=None):
         return reverse('api:workflow_job_node_detail', kwargs={'pk': self.pk}, request=request)
 
@@ -620,6 +624,10 @@ class WorkflowJob(UnifiedJob, WorkflowJobOptions, SurveyJobMixin, JobNotificatio
     def workflow_nodes(self):
         return self.workflow_job_nodes
 
+    @property
+    def event_processing_finished(self):
+        return True
+
     def _get_parent_field_name(self):
         if self.job_template_id:
             # This is a workflow job which is a container for slice jobs