8725 Update TCP's RTO even if incoming segment's TSecr is 0
Reviewed by: Dan McDonald <danmcd@joyent.com>
Reviewed by: ken mays <maybird1776@yahoo.com>
Reviewed by: Toomas Soome <tsoome@me.com>

*** 4303,4318 ****
          if ((tcp->tcp_valid_bits & TCP_URG_VALID) &&
              SEQ_GT(seg_ack, tcp->tcp_urg))
                  tcp->tcp_valid_bits &= ~TCP_URG_VALID;
  
          /* Can we update the RTT estimates? */
!         if (tcp->tcp_snd_ts_ok) {
!                 /* Ignore zero timestamp echo-reply. */
!                 if (tcpopt.tcp_opt_ts_ecr != 0) {
                          tcp_set_rto(tcp, (int32_t)LBOLT_FASTPATH -
                              (int32_t)tcpopt.tcp_opt_ts_ecr);
-                 }
  
                  /* If needed, restart the timer. */
                  if (tcp->tcp_set_timer == 1) {
                          TCP_TIMER_RESTART(tcp, tcp->tcp_rto);
                          tcp->tcp_set_timer = 0;
--- 4303,4315 ----
          if ((tcp->tcp_valid_bits & TCP_URG_VALID) &&
              SEQ_GT(seg_ack, tcp->tcp_urg))
                  tcp->tcp_valid_bits &= ~TCP_URG_VALID;
  
          /* Can we update the RTT estimates? */
!         if (tcp->tcp_snd_ts_ok && tcpopt.tcp_opt_ts_ecr != 0) {
                  tcp_set_rto(tcp, (int32_t)LBOLT_FASTPATH -
                      (int32_t)tcpopt.tcp_opt_ts_ecr);
  
                  /* If needed, restart the timer. */
                  if (tcp->tcp_set_timer == 1) {
                          TCP_TIMER_RESTART(tcp, tcp->tcp_rto);
                          tcp->tcp_set_timer = 0;