Refresh pending retransmit timer when timestamp RTT changes

src/transport_layer/etcp.c

@@ -1473,6 +1473,7 @@ void etcp_conn_input(struct ETCP_DGRAM* pkt) {
                         etcp->last_rtt_cb_time = now_tb;
                     }
                 }
+                if (new_rtt != prev_rtt) etcp_tx_update_rto(pkt->link);
                 break;
             }
             case ETCP_SECTION_PAYLOAD: {