[IPV6]: Simplify IPv6 control sockets creation.

Do this by replacing sock_create_kern with inet_ctl_sock_create.

Signed-off-by: Denis V. Lunev <den@openvz.org>
Acked-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>