Fix for connected device files saving after check for existing connector

thingsboard_gateway/gateway/tb_gateway_service.py

@@ -1872,6 +1872,7 @@ def __load_persistent_devices(self):
                 except Exception as e:
                     log.exception(e)
                     continue
+            self.__save_persistent_devices()
         else:
             log.debug("No device found in connected device file.")
             self.__connected_devices = {} if self.__connected_devices is None else self.__connected_devices