WIP: supplicant: Store assigned addr for P2P group joins
This is completely untested right now (and, I am not sure I have HW to test it). But, I would appreciate a quick look whether the approach to use nm_device_set_dev2_ip_config
and how to pass the addresses around is correct in principle.
A P2P Group Owner may assign an IP address and netmask to us. Store this address so that it can be retrieved later during the IP configuration stage.