Fix bug by using cancel_flag.

awx/main/models/workflow.py

@@ -423,8 +423,3 @@ class WorkflowJob(UnifiedJob, WorkflowJobOptions, JobNotificationMixin, Workflow
     '''
     def start_celery_task(self, opts, error_callback, success_callback):
         return None
-
-    def cancel(self):
-        if self.can_cancel:
-            self.status = 'canceled'
-            self.save(update_fields=['status'])

awx/main/scheduler/__init__.py

@@ -130,8 +130,11 @@ class TaskManager():
     def process_finished_workflow_jobs(self, workflow_jobs):
         for workflow_job in workflow_jobs:
             dag = WorkflowDAG(workflow_job)
-            if workflow_job.status == 'canceled':
+            if workflow_job.cancel_flag:
+                workflow_job.status = 'canceled'
+                workflow_job.save()
                 dag.bfs_nodes_to_cancel()
+                connection.on_commit(lambda: workflow_job.websocket_emit_status(workflow_job.status))
             elif dag.is_workflow_done():
                 if workflow_job._has_failed():
                     workflow_job.status = 'failed'