Avoid double call to set ofono's online property

On initialization a double call to set-soft was being done for the ofono device. This caused bugs LP #1392397 and #1379807.
Add an if (!URF_IS_OFONO_DEVICE (user_data)) return; here, and it should be sufficient to guard against running the callback after the device was freed, for the one call that might happen after freeing the device.