added back err to redis flushdb

src/database/redis.js

@@ -118,7 +118,7 @@
 	module.flushdb = function(callback) {
 		redisClient.send_command('flushdb', [], function(err) {
 			if (typeof callback === 'function') {
-				callback();
+				callback(err);
 			}
 		});
 	};