netfilter: netns ebtables: part 1

* propagate netns from userspace, register table in passed netns
* remporarily register every ebt_table in init_net

P. S.: one needs to add ".netns_ok = 1" to igmp_protocol to test with
ebtables(8) in netns.

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Patrick McHardy <kaber@trash.net>
diff --git a/net/bridge/netfilter/ebtable_nat.c b/net/bridge/netfilter/ebtable_nat.c
index f60c1e7..bafe160 100644
--- a/net/bridge/netfilter/ebtable_nat.c
+++ b/net/bridge/netfilter/ebtable_nat.c
@@ -102,7 +102,7 @@
 {
 	int ret;
 
-	ret = ebt_register_table(&frame_nat);
+	ret = ebt_register_table(&init_net, &frame_nat);
 	if (ret < 0)
 		return ret;
 	ret = nf_register_hooks(ebt_ops_nat, ARRAY_SIZE(ebt_ops_nat));