add function to update broker token

ml/thing.py

@@ -426,17 +426,21 @@ def receive():
             threading.Thread(target=receive).start()
 
         else:
-            self.broker = Broker(
-                auth_form="Username/Password",
-                username=" ",
-                password=self.__access_token,
-                host=BaseVariable.BROKER_HOST,
-            )
+            if self.broker is None:
+                # first time to build a broker instance
+                self.broker = Broker(
+                    auth_form="Username/Password",
+                    username=" ",
+                    password=self.__access_token,
+                    host=BaseVariable.BROKER_HOST,
+                )
 
-            threading.Thread(
-                target=self.broker.receive,
-                args=(self.__endpoint, self.__on_broker_callback),
-            ).start()
+                threading.Thread(
+                    target=self.broker.receive,
+                    args=(self.__endpoint, self.__on_broker_callback),
+                ).start()
+            else:
+                self.broker.update_token(self.access_token)
 
     def __on_broker_callback(self, ch, method, properties, body):
         """Parses body (content of a S3I-B message) and delegates the