MINOR: mux-quic: properly initialize qcc flags

Set qcc.flags to 0 on qc_init.
diff --git a/src/mux_quic.c b/src/mux_quic.c
index 5218709..bdb15ce 100644
--- a/src/mux_quic.c
+++ b/src/mux_quic.c
@@ -400,6 +400,7 @@
 
 	qcc->conn = conn;
 	conn->ctx = qcc;
+	qcc->flags = 0;
 
 	qcc->app_ops = NULL;