config-changed always closes and then reopens all the ports

Hi,

update_service_ports() is called with a list of strings for old ports, and a tuple of ints for new ports - leading to all ports getting closed then opened.

The bug is here :

    old_service_ports = []
    for port_plus_proto in opened_ports():
        # opened_ports returns e.g. ['22/tcp', '53/udp']
        # but we just want the port numbers, as ints
        if port_plus_proto.endswith('/tcp') or port_plus_proto.endswith('/udp'):
            port_only = port_plus_proto[:-4]
            old_service_ports.append(port_only)
        else:
            raise ValueError('{} is not a valid port/proto value'.format(port_plus_proto))

We need to append "int(port_only)" to get ints.