rc: make qos-start run in blocking mode

Since QoS config gets applied immediately after rather than
before calling this script, ensure it has all the necessary
time to complete its own changes to QoS settings.

release/src/router/rc/qos.c

@@ -1395,7 +1395,7 @@ static int start_tqos(void)
 
 	fclose(f);
 	chmod(qosfn, 0700);
-	run_custom_script("qos-start", 0, "init", NULL);
+	run_custom_script("qos-start", 120, "init", NULL);
 	eval((char *)qosfn, "start");
 	QOSDBG("[qos] tc done!\n");
 
@@ -2792,7 +2792,7 @@ int start_cake(void)
 	fclose(f);
 	chmod("/etc/cake-qos.conf", 0755);
 	chmod(qosfn, 0755);
-	run_custom_script("qos-start", 0, "init", NULL);
+	run_custom_script("qos-start", 120, "init", NULL);
 	eval((char *)qosfn, "start");
 
 	return 0;