net, ip6_tunnel: fix namespaces move

in the same manner as commit d0f4185160 ("net, ip_tunnel: fix
namespaces move"), fix namespace moving as it was broken since commit
8d79266bc4 ("ip6_tunnel: add collect_md mode to IPv6 tunnel"), but for
ipv6 this time; there is no reason to keep it for ip6_tunnel.

Fixes: 8d79266bc4 ("ip6_tunnel: add collect_md mode to IPv6 tunnel")
Signed-off-by: William Dauchy <w.dauchy@criteo.com>
Acked-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv6/ip6_tunnel.c

@@ -1877,10 +1877,8 @@ static int ip6_tnl_dev_init(struct net_device *dev)
 	if (err)
 		return err;
 	ip6_tnl_link_config(t);
-	if (t->parms.collect_md) {
-		dev->features |= NETIF_F_NETNS_LOCAL;
+	if (t->parms.collect_md)
 		netif_keep_dst(dev);
-	}
 	return 0;
 }