MINOR: quic: Prepare Application level packet asap.

It is possible the TLS stack stack provides us with 1-RTT TX secrets
at the same time as Handshake secrets are provided. Thanks to this
simple patch we can build Application level packets during the handshake.
diff --git a/src/xprt_quic.c b/src/xprt_quic.c
index 634c553..af0381a 100644
--- a/src/xprt_quic.c
+++ b/src/xprt_quic.c
@@ -2116,6 +2116,9 @@
 			if ((tel == QUIC_TLS_ENC_LEVEL_INITIAL || tel == QUIC_TLS_ENC_LEVEL_HANDSHAKE) &&
 			    (MT_LIST_ISEMPTY(&qel->pktns->tx.frms) ||
 			     (next_tel != QUIC_TLS_ENC_LEVEL_NONE && qc->els[next_tel].pktns->tx.in_flight))) {
+				/* If QUIC_TLS_ENC_LEVEL_HANDSHAKE was already reached let's try QUIC_TLS_ENC_LEVEL_APP */
+				if (tel == QUIC_TLS_ENC_LEVEL_HANDSHAKE && next_tel == tel)
+					next_tel = QUIC_TLS_ENC_LEVEL_APP;
 				tel = next_tel;
 				qel = &qc->els[tel];
 				if (!MT_LIST_ISEMPTY(&qel->pktns->tx.frms)) {