BUG/MINOR: quic: Do not use ack delay during the handshakes

As revealed by GH haproxy#2120 opened by @Tristan971, there are cases where ACKs
have to be sent without packet to acknowledge because the ACK timer has
been triggered and the connection needs to probe the peer at the same time.
Indeed

Thank you to @Tristan971 for having reported this issue.

Must be backported to 2.6 and 2.7.

Author: haproxyFred

src/quic_conn.c

@@ -4505,9 +4505,13 @@ int qc_treat_rx_pkts(struct quic_conn *qc, struct quic_enc_level *cur_el,
 				struct quic_arng ar = { .first = pkt->pn, .last = pkt->pn };
 
 				if (pkt->flags & QUIC_FL_RX_PACKET_ACK_ELICITING) {
+					int arm_ack_timer =
+						qc->state >= QUIC_HS_ST_COMPLETE &&
+						qel->pktns == &qc->pktns[QUIC_TLS_PKTNS_01RTT];
+
 					qel->pktns->flags |= QUIC_FL_PKTNS_ACK_REQUIRED;
 					qel->pktns->rx.nb_aepkts_since_last_ack++;
-					qc_idle_timer_rearm(qc, 1, 1);
+					qc_idle_timer_rearm(qc, 1, arm_ack_timer);
 				}
 				if (pkt->pn > largest_pn) {
 					largest_pn = pkt->pn;