a lot of thread housekeeping. Switch them off when not needed / disabled.

src/modules/ExternalNotificationModule.cpp

@@ -199,6 +199,7 @@ ExternalNotificationModule::ExternalNotificationModule()
         }
     } else {
         DEBUG_MSG("External Notification Module Disabled\n");
+        setInterval(INT32_MAX);
         enabled = false;
     }
 }