valgrind: fix small leak in cgroup

src/lxc/cgroup.c

@@ -1614,6 +1614,7 @@ void lxc_cgroup_hierarchy_free(struct cgroup_hierarchy *h)
 	if (!h)
 		return;
 	lxc_free_array((void **)h->subsystems, free);
+	free(h->all_mount_points);
 	free(h);
 }