netfilter: nfnetlink_queue: autoload nf_conntrack_netlink module NFQA_CFG_F_CONNTRACK config flag

This patch enables to load nf_conntrack_netlink module if
NFQA_CFG_F_CONNTRACK config flag is specified.

Signed-off-by: Ken-ichirou MATSUZAWA <chamas@h4.dion.ne.jp>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>