[IPIP]: Allow for IPPROTO_IPIP protocol in namespaces.

This one was disabled by default for sanity.
Signed-off-by: NPavel Emelyanov <xemul@openvz.org>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/ipv4/tunnel4.c

@@ -136,6 +136,7 @@ static struct net_protocol tunnel4_protocol = {
 	.handler	=	tunnel4_rcv,
 	.err_handler	=	tunnel4_err,
 	.no_policy	=	1,
+	.netns_ok	=	1,
 };
 
 #if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)