pstree: Add more debug output for prepare_pstree_kobj_ids

Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

pstree.c

@@ -544,6 +544,7 @@ set_mask:
 		}
 	}
 
+	pr_debug("NS mask to use %lx\n", current_ns_mask);
 	return 0;
 }