cleanup group membership on disconnect

* zcard asgi::group:jobs-status_changed <-- to see a group set that
continues to grow. Issue this command in a loop while refreshing the
browser page on the jobs list. Before this change the set size would
continue to grow as daphne channel names are added to the group. After
this change the set size stays stable at the expected, 1.

awx/main/consumers.py

@@ -108,6 +108,7 @@ class BroadcastConsumer(AsyncJsonWebsocketConsumer):
     async def disconnect(self, code):
         # TODO: log ip of disconnected client
         logger.info("Client disconnected")
+        await self.channel_layer.group_discard(settings.BROADCAST_WEBSOCKET_GROUP_NAME, self.channel_name)
 
     async def internal_message(self, event):
         await self.send(event['text'])
@@ -132,6 +133,14 @@ class EventConsumer(AsyncJsonWebsocketConsumer):
             await self.send_json({"close": True})
             await self.close()
 
+    async def disconnect(self, code):
+        current_groups = set(self.scope['session'].pop('groups') if 'groups' in self.scope['session'] else [])
+        for group_name in current_groups:
+            await self.channel_layer.group_discard(
+                group_name,
+                self.channel_name,
+            )
+
     @database_sync_to_async
     def user_can_see_object_id(self, user_access, oid):
         # At this point user is a channels.auth.UserLazyObject object