Update mqtt_source.yaml

Change to the default MQTT server address.

etc/mqtt_source.yaml

@@ -2,11 +2,11 @@
 default:
   qos: 1
   sharedsubscription: true
-  servers: [tcp://10.211.55.6:1887]
+  servers: [tcp://127.0.0.1:1887]
   #TODO: Other global configurations
 
 
 #Override the global configurations
 demo_conf: #Conf_key
   qos: 0
-  servers: [tcp://10.211.55.6:1883, tcp://127.0.0.1]
+  servers: [tcp://10.211.55.6:1883, tcp://127.0.0.1]