Better support for setting up and removing private cgroups

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/fio.c b/fio.c
index 4bbab5a..a18ca1b 100644
--- a/fio.c
+++ b/fio.c
@@ -1668,6 +1668,8 @@
 		}
 	}
 
+	cgroup_kill();
+
 	fio_mutex_remove(startup_mutex);
 	fio_mutex_remove(writeout_mutex);
 	return exit_value;