[NETFILTER]: CONNMARK target needs ip_conntrack

There's a missing dependency from the CONNMARK target to ip_conntrack.

Signed-off-by: Pablo Neira Ayuso <pablo@eurodev.net>
Signed-off-by: Harald Welte <laforge@netfilter.org>
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>