netfilter: xtables: add struct xt_mtdtor_param::net

Add ->net to match destructor list like ->net in constructor list.

Make sure it's set in ebtables/iptables/ip6tables, this requires to
propagate netns up to *_unregister_table().

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Patrick McHardy <kaber@trash.net>
diff --git a/net/ipv4/netfilter/nf_nat_rule.c b/net/ipv4/netfilter/nf_nat_rule.c
index 9e81e0d..85da34f 100644
--- a/net/ipv4/netfilter/nf_nat_rule.c
+++ b/net/ipv4/netfilter/nf_nat_rule.c
@@ -195,7 +195,7 @@
 
 static void __net_exit nf_nat_rule_net_exit(struct net *net)
 {
-	ipt_unregister_table(net->ipv4.nat_table);
+	ipt_unregister_table(net, net->ipv4.nat_table);
 }
 
 static struct pernet_operations nf_nat_rule_net_ops = {