[TCP]: Restore over-zealous tcp_sync_left_out-like removals

tcp_verify_left_out is useful for verifying S+L condition, so
add it back to couple of places in where the code was not
calling to tcp_sync_left_out but used own ad-hoc solution
(before the tcp_sync_left_out got removed).
Signed-off-by: NIlpo Järvinen <ilpo.jarvinen@helsinki.fi>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/ipv4/tcp_input.c

@@ -1346,6 +1346,8 @@ tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb, u32 prior_snd_
 		}
 	}
 
+	tcp_verify_left_out(tp);
+
 	if ((reord < tp->fackets_out) && icsk->icsk_ca_state != TCP_CA_Loss &&
 	    (!tp->frto_highmark || after(tp->snd_una, tp->frto_highmark)))
 		tcp_update_reordering(sk, ((tp->fackets_out + 1) - reord), 0);
@@ -2121,6 +2123,8 @@ static void tcp_try_to_open(struct sock *sk, int flag)
 {
 	struct tcp_sock *tp = tcp_sk(sk);
 
+	tcp_verify_left_out(tp);
+
 	if (tp->retrans_out == 0)
 		tp->retrans_stamp = 0;