[NET]: Make rtnetlink infrastructure network namespace aware (v3)

After this patch none of the netlink callback support anything
except the initial network namespace but the rtnetlink infrastructure
now handles multiple network namespaces.

Changes from v2:
- IPv6 addrlabel processing

Changes from v1:
- no need for special rtnl_unlock handling
- fixed IPv6 ndisc

Signed-off-by: Denis V. Lunev <den@openvz.org>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index 1d28395..e4b6fb4 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -2610,7 +2610,7 @@
 	if (err <= 0)
 		goto errout_free;
 
-	err = rtnl_unicast(skb, NETLINK_CB(in_skb).pid);
+	err = rtnl_unicast(skb, &init_net, NETLINK_CB(in_skb).pid);
 errout:
 	return err;