net: fix __skb_try_recv_from_queue to return the old behavior
This function has to return NULL on a error case, because there is a
separate error variable.
The offset has to be changed only if skb is returned
v2: fix udp code to not use an extra variable
Cc: Paolo Abeni <pabeni@redhat.com> Cc: Eric Dumazet <edumazet@google.com> Cc: David S. Miller <davem@davemloft.net> Fixes: 79f3a5466530 ("net/sock: factor out dequeue/peek with offset cod") Signed-off-by: Andrei Vagin <avagin@openvz.org> Acked-by: Paolo Abeni <pabeni@redhat.com> Signed-off-by: David S. Miller <davem@davemloft.net>