log mac address when updating it

pyheatpump/config.py

@@ -72,6 +72,7 @@ def mac_address_init():
     addr = ifaddresses(interface)[AF_LINK][0]['addr']
     config.set('heatpump', 'mac_address', addr)
     save_config()
+    logger.info('Got new mac address {addr}')
     return addr