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.
After freeing the device, user_data points to random rubbish. URF_IS_OFONO_DEVICE dereferences user_data to retrieve its GObject->g_class value and compare it with URF_TYPE_DEVICE_OFONO, so you cannot do that.