MINOR: quic: Do not try to treat 0-RTT packets without started mux

We proceed the same was as for 1-RTT packets: we do not try to treat
them until the mux is started.
diff --git a/src/xprt_quic.c b/src/xprt_quic.c
index d7e6805..6537f04 100644
--- a/src/xprt_quic.c
+++ b/src/xprt_quic.c
@@ -3204,7 +3204,8 @@
 		return 0;
 
 	/* check if the connection layer is ready before using app level */
-	if (tel == QUIC_TLS_ENC_LEVEL_APP && qc->mux_state != QC_MUX_READY)
+	if ((tel == QUIC_TLS_ENC_LEVEL_APP || tel == QUIC_TLS_ENC_LEVEL_EARLY_DATA) &&
+	    qc->mux_state != QC_MUX_READY)
 		return 0;
 
 	return 1;