[IPV6]: Fix ip6_copy_metadata potential dst leak too.

Same fix as per ipv4 ip_copy_metadata().
Signed-off-by: Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv6/ip6_output.c

@@ -463,6 +463,7 @@ static void ip6_copy_metadata(struct sk_buff *to, struct sk_buff *from)
 	to->priority = from->priority;
 	to->protocol = from->protocol;
 	to->security = from->security;
+	dst_release(to->dst);
 	to->dst = dst_clone(from->dst);
 	to->dev = from->dev;