BUG/MINOR: quic: 1RTT packets ignored after mux was released

We must be able to handle 1RTT packets after the mux has terminated its job
(qc->mux_state == QC_MUX_RELEASED). So the condition (qc->mux_state != QC_MUX_READY)
in qc_qel_may_rm_hp() is not correct when we want to wait for the mux to be started.
Add a check in qc_parse_pkt_frms() to ensure is started before calling it. All
the STREAM frames will be ignored when the mux will be released.
diff --git a/src/xprt_quic.c b/src/xprt_quic.c
index 3e4dd92..b9723d9 100644
--- a/src/xprt_quic.c
+++ b/src/xprt_quic.c
@@ -2428,6 +2428,10 @@
 			} else if (!(stream->id & QUIC_STREAM_FRAME_ID_INITIATOR_BIT))
 				goto err;
 
+			/* At the application layer the connection may have already been closed. */
+			if (qc->mux_state != QC_MUX_READY)
+				break;
+
 			if (!qc_handle_strm_frm(pkt, stream, qc))
 				goto err;
 
@@ -3374,7 +3378,7 @@
 
 	/* check if the connection layer is ready before using app level */
 	if ((tel == QUIC_TLS_ENC_LEVEL_APP || tel == QUIC_TLS_ENC_LEVEL_EARLY_DATA) &&
-	    qc->mux_state != QC_MUX_READY)
+	    qc->mux_state == QC_MUX_NULL)
 		return 0;
 
 	return 1;