tcp: fix under-evaluated ssthresh in TCP Vegas

With the commit 76174004 (tcp: do not slow start when cwnd equals
ssthresh), the comparison to the reduced cwnd in tcp_vegas_ssthresh() would
under-evaluate the ssthresh.
Signed-off-by: NHoang Tran <hoang.tran@uclouvain.be>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/ipv4/tcp_vegas.c

@@ -158,7 +158,7 @@ EXPORT_SYMBOL_GPL(tcp_vegas_cwnd_event);
 
 static inline u32 tcp_vegas_ssthresh(struct tcp_sock *tp)
 {
-	return  min(tp->snd_ssthresh, tp->snd_cwnd-1);
+	return  min(tp->snd_ssthresh, tp->snd_cwnd);
 }
 
 static void tcp_vegas_cong_avoid(struct sock *sk, u32 ack, u32 acked)