1) If sk_filter() is applied, skb was leaked (not freed)
2) Testing SOCK_DEAD twice is racy :
   packet could be freed while already queued.
3) Remove obsolete comment about caching skb->len
Signed-off-by: NEric Dumazet <edumazet@google.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>