netfilter: ctnetlink: fix module auto-load in ctnetlink_parse_nat

(c7232c99 netfilter: add protocol independent NAT core) added
incorrect locking for the module auto-load case in ctnetlink_parse_nat.

That function is always called from ctnetlink_create_conntrack which
requires no locking.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

net/netfilter/nf_conntrack_netlink.c

@@ -1120,16 +1120,13 @@ ctnetlink_parse_nat_setup(struct nf_conn *ct,
 	if (err == -EAGAIN) {
 #ifdef CONFIG_MODULES
 		rcu_read_unlock();
-		spin_unlock_bh(&nf_conntrack_lock);
 		nfnl_unlock();
 		if (request_module("nf-nat-%u", nf_ct_l3num(ct)) < 0) {
 			nfnl_lock();
-			spin_lock_bh(&nf_conntrack_lock);
 			rcu_read_lock();
 			return -EOPNOTSUPP;
 		}
 		nfnl_lock();
-		spin_lock_bh(&nf_conntrack_lock);
 		rcu_read_lock();
 #else
 		err = -EOPNOTSUPP;