use set to get groups

src/groups.js

@@ -105,8 +105,8 @@ var async = require('async'),
 		}
 	};
 
-	Groups.getGroups = function(start, stop, callback) {
-		db.getSortedSetRevRange('groups:createtime', start, stop, callback);
+	Groups.getGroups = function(set, start, stop, callback) {
+		db.getSortedSetRevRange(set, start, stop, callback);
 	};
 
 	Groups.get = function(groupName, options, callback) {

src/privileges/categories.js

@@ -92,7 +92,7 @@ module.exports = function(privileges) {
 						}), next);
 					},
 					function(memberSets, next) {
-						groups.getGroups(0, -1, function(err, groupNames) {
+						groups.getGroups('groups:createtime', 0, -1, function(err, groupNames) {
 							if (err) {
 								return next(err);
 							}