P2P: Do not clear wpa_s->go_dev_addr before group removal

P2P: Do not clear wpa_s->go_dev_addr before group removal

This variable is needed to figure out whether a wpa_supplicant interface
is for a P2P group that is (or was) connected to a specific GO. The
previous implementation was able to find such a case only when there was
an association with the GO. However, this may be needed even if there is
a temporary disconnection from the GO. Keep the GO device address
information over such temporary disconnections and only remove it on
group termination. This fixes an issue with D-Bus Peer PropertiesChanged
signals for the Groups property in case a P2P group gets removed due to
group idle timeout instead of explicit group termination command (local
request) or GO notification.

Signed-off-by: Jouni Malinen <j@w1.fi>