netfilter: netns nf_conntrack: per-netns conntrack hash

* make per-netns conntrack hash

  Other solution is to add ->ct_net pointer to tuplehashes and still has one
  hash, I tried that it's ugly and requires more code deep down in protocol
  modules et al.

* propagate netns pointer to where needed, e. g. to conntrack iterators.

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Patrick McHardy <kaber@trash.net>
diff --git a/include/net/netns/conntrack.h b/include/net/netns/conntrack.h
index edf8471..b767683 100644
--- a/include/net/netns/conntrack.h
+++ b/include/net/netns/conntrack.h
@@ -5,5 +5,7 @@
 
 struct netns_ct {
 	atomic_t		count;
+	struct hlist_head	*hash;
+	int			hash_vmalloc;
 };
 #endif