Fix lxc.cgroup2.<controller> on cgroup2-only systems

src/lxc/cgroups/cgfsng.c

@@ -2684,6 +2684,7 @@ static int cg_unified_init(struct cgroup_ops *ops, bool relative,
 		cg_unified_delegate(&new->cgroup2_chown);
 
 	ops->cgroup_layout = CGROUP_LAYOUT_UNIFIED;
+	ops->unified = new;
 	return CGROUP2_SUPER_MAGIC;
 }