BUG/MINOR: quic: wake up MUX on probing only for 01RTT

On PTO probe timeout expiration, a probe packet must be emitted.
quic_pto_pktns() is used to determine for which packet space the timer
has expired. However, if MUX is already subscribed for sending, it is
woken up without checking first if this happened for the 01RTT packet
space.

It is unsure that this is really a bug as in most cases, MUX is
established only after Initial and Handshake packet spaces are removed.
However, the situation is not se clear when 0-RTT is used. For this
reason, adjust the code to explicitely check for the 01RTT packet space
before waking up the MUX layer.

This should be backported up to 2.6. Note that qc_notify_send() does not
exists in 2.6 so it should be replaced by the explicit block checking
(qc->subs && qc->subs->events & SUB_RETRY_SEND).
diff --git a/src/quic_conn.c b/src/quic_conn.c
index c67ae6d..529e997 100644
--- a/src/quic_conn.c
+++ b/src/quic_conn.c
@@ -5158,40 +5158,38 @@
 
 	if (qc->path->in_flight) {
 		pktns = quic_pto_pktns(qc, qc->state >= QUIC_HS_ST_CONFIRMED, NULL);
-		if (qc_notify_send(qc)) {
-			pktns->tx.pto_probe = QUIC_MAX_NB_PTO_DGRAMS;
+		if (pktns == &qc->pktns[QUIC_TLS_PKTNS_INITIAL]) {
+			if (qc_may_probe_ipktns(qc)) {
+				qc->flags |= QUIC_FL_CONN_RETRANS_NEEDED;
+				pktns->flags |= QUIC_FL_PKTNS_PROBE_NEEDED;
+				TRACE_STATE("needs to probe Initial packet number space", QUIC_EV_CONN_TXPKT, qc);
+			}
+			else {
+				TRACE_STATE("Cannot probe Initial packet number space", QUIC_EV_CONN_TXPKT, qc);
+			}
+			if (qc->pktns[QUIC_TLS_PKTNS_HANDSHAKE].tx.in_flight) {
+				qc->flags |= QUIC_FL_CONN_RETRANS_NEEDED;
+				qc->pktns[QUIC_TLS_PKTNS_HANDSHAKE].flags |= QUIC_FL_PKTNS_PROBE_NEEDED;
+				TRACE_STATE("needs to probe Handshake packet number space", QUIC_EV_CONN_TXPKT, qc);
+			}
 		}
-		else {
-			if (pktns == &qc->pktns[QUIC_TLS_PKTNS_INITIAL]) {
+		else if (pktns == &qc->pktns[QUIC_TLS_PKTNS_HANDSHAKE]) {
+			TRACE_STATE("needs to probe Handshake packet number space", QUIC_EV_CONN_TXPKT, qc);
+			qc->flags |= QUIC_FL_CONN_RETRANS_NEEDED;
+			pktns->flags |= QUIC_FL_PKTNS_PROBE_NEEDED;
+			if (qc->pktns[QUIC_TLS_PKTNS_INITIAL].tx.in_flight) {
 				if (qc_may_probe_ipktns(qc)) {
-					qc->flags |= QUIC_FL_CONN_RETRANS_NEEDED;
-					pktns->flags |= QUIC_FL_PKTNS_PROBE_NEEDED;
+					qc->pktns[QUIC_TLS_PKTNS_INITIAL].flags |= QUIC_FL_PKTNS_PROBE_NEEDED;
 					TRACE_STATE("needs to probe Initial packet number space", QUIC_EV_CONN_TXPKT, qc);
 				}
 				else {
 					TRACE_STATE("Cannot probe Initial packet number space", QUIC_EV_CONN_TXPKT, qc);
 				}
-				if (qc->pktns[QUIC_TLS_PKTNS_HANDSHAKE].tx.in_flight) {
-					qc->flags |= QUIC_FL_CONN_RETRANS_NEEDED;
-					qc->pktns[QUIC_TLS_PKTNS_HANDSHAKE].flags |= QUIC_FL_PKTNS_PROBE_NEEDED;
-					TRACE_STATE("needs to probe Handshake packet number space", QUIC_EV_CONN_TXPKT, qc);
-				}
 			}
-			else if (pktns == &qc->pktns[QUIC_TLS_PKTNS_HANDSHAKE]) {
-				TRACE_STATE("needs to probe Handshake packet number space", QUIC_EV_CONN_TXPKT, qc);
-				qc->flags |= QUIC_FL_CONN_RETRANS_NEEDED;
-				pktns->flags |= QUIC_FL_PKTNS_PROBE_NEEDED;
-				if (qc->pktns[QUIC_TLS_PKTNS_INITIAL].tx.in_flight) {
-					if (qc_may_probe_ipktns(qc)) {
-						qc->pktns[QUIC_TLS_PKTNS_INITIAL].flags |= QUIC_FL_PKTNS_PROBE_NEEDED;
-						TRACE_STATE("needs to probe Initial packet number space", QUIC_EV_CONN_TXPKT, qc);
-					}
-					else {
-						TRACE_STATE("Cannot probe Initial packet number space", QUIC_EV_CONN_TXPKT, qc);
-					}
-				}
-			}
-			else if (pktns == &qc->pktns[QUIC_TLS_PKTNS_01RTT]) {
+		}
+		else if (pktns == &qc->pktns[QUIC_TLS_PKTNS_01RTT]) {
+			/* Wake up upper layer if waiting to send new data. */
+			if (!qc_notify_send(qc)) {
 				TRACE_STATE("needs to probe 01RTT packet number space", QUIC_EV_CONN_TXPKT, qc);
 				qc->flags |= QUIC_FL_CONN_RETRANS_NEEDED;
 				pktns->flags |= QUIC_FL_PKTNS_PROBE_NEEDED;