fix auth fail

Author: adrai

lib/databases/mongodb.js

@@ -53,10 +53,10 @@ var MongoSessionStore = function(options, callback) {
         if (err) {
             if (callback) callback(err);
         } else {
-            var finish = function() {
+            var finish = function(err) {
                 self.client = client;
                 self.sessions = new mongo.Collection(client, options.collectionName);
-                if (callback) callback(null, self);
+                if (callback) callback(err, self);
             };
 
             if (options.username) {