bearer-mbim: IP type may be reported as deactivated and still have IP settings

If we were requesting for IPv4v6 and we only got IPv4 reported as activated, we would right away ignore the IPv6 bits, even if we received IPv6 settings later on when querying for them. Change that, so that if an IP address of a given type is received, we assume the corresponding context was really activated even if the modem didn't report it in the connect set response.

Fixes #320 (closed)