MINOR: mux-h1: do not even try to receive if the connection is not fully set up

If the connection is still waiting for L4/L6, there's no point even trying
to receive as it will fail, so better return zero in h1_recv_allowed().
diff --git a/src/mux_h1.c b/src/mux_h1.c
index b3fa8f5..ea52119 100644
--- a/src/mux_h1.c
+++ b/src/mux_h1.c
@@ -363,8 +363,8 @@
 		return 0;
 	}
 
-	if (h1c->conn->flags & (CO_FL_ERROR|CO_FL_SOCK_RD_SH)) {
-		TRACE_DEVEL("recv not allowed because of (error|read0) on connection", H1_EV_H1C_RECV|H1_EV_H1C_BLK, h1c->conn);
+	if (h1c->conn->flags & (CO_FL_ERROR|CO_FL_SOCK_RD_SH|CO_FL_WAIT_L4_CONN|CO_FL_WAIT_L6_CONN)) {
+		TRACE_DEVEL("recv not allowed because of (error|read0|waitl4|waitl6) on connection", H1_EV_H1C_RECV|H1_EV_H1C_BLK, h1c->conn);
 		return 0;
 	}