Revert "netfilter: ipv6: nf_defrag: drop skb dst before queueing"

This reverts commit 28c74ff8.

From Florian Westphal <fw@strlen.de>:

	It causes kernel crash for locally generated ipv6 fragments
	when netfilter ipv6 defragmentation is used.

	The faulty commit is not essential for -stable, it only
	delays netns teardown for longer than needed when that netns
	still has ipv6 frags queued.  Much better than crash :-/
Signed-off-by: Sasha Levin <sashal@kernel.org>

net/ipv6/netfilter/nf_conntrack_reasm.c

@@ -598,8 +598,6 @@ int nf_ct_frag6_gather(struct net *net, struct sk_buff *skb, u32 user)
 	    fq->q.meat == fq->q.len &&
 	    nf_ct_frag6_reasm(fq, skb, dev))
 		ret = 0;
-	else
-		skb_dst_drop(skb);
 
 out_unlock:
 	spin_unlock_bh(&fq->q.lock);