rds: Calling getsockname() on unbounded socket generates seg fault

rds: Calling getsockname() on unbounded socket generates seg fault

If a socket is not yet bound, calling getsockname() should return an
unspecified address with family AF_UNSPEC as an RDS socket can be
bound to either an IPv4 or an IPv6 address.  Hence returning either
family is incorrect.  Currently, the returned address is set to an
unspecified address with family AF_INET6.  If the passed in buffer is
smaller than sizeof(struct sockaddr_in6), the app may get a
segmentation fault error.  This is similar to passing a buffer smaller
than sizeof(struct sockaddr_in) before the IPv6 changes.

Orabug: 27463484

Signed-off-by: Ka-Cheong Poon <ka-cheong.poon@oracle.com>
Reviewed-by: Darren Kenny <darren.kenny@oracle.com>
Reviewed-by: Håkon Bugge <haakon.bugge@oracle.com>