Unlock SIOCGIFG{MEMB,ATTR,LIST}

Unlock SIOCGIFG{MEMB,ATTR,LIST}

The global interface group list is also protected by the net lock and all
access to it (all within if.c) take it accordingly.

Getting all
- members    of a group (SIOCGIFGMEMB),
- attributes of a group (SIOCGIFGATTR),
- groups                (SIOCGIFGLIST)
are each read-only operations on the global interface group `ifg_head'.

The global interface list `ifnetlist' or its per-interface group lists are
not used in these ioctls.

OK mvs