seize: collect_pstree -- Add missing error sign return

If we can't freeze process don't forget to return
error sign, otherwise we continue operating over
nonfrozen processes, leading into various errors.
Signed-off-by: Cyrill Gorcunov <gorcunov@virtuozzo.com>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>

criu/seize.c

@@ -765,8 +765,10 @@ int collect_pstree(void)
 	if (ret < 0)
 		goto err;
 
-	if (opts.freeze_cgroup && freezer_wait_processes())
+	if (opts.freeze_cgroup && freezer_wait_processes()) {
+		ret = -1;
 		goto err;
+	}
 
 	ret = 0;
 	timing_stop(TIME_FREEZING);