fix tests

src/test/system-test.js

@@ -6,28 +6,13 @@
 
 'use strict';
 
-const async = require('async'),
-    database = require('../database.js'),
+const common = require('./common.js'),
     expect = require('expect.js'),
     system = require('../system.js');
 
-function setup(done) {
-    async.series([
-        database.initialize,
-        database._clear
-    ], done);
-}
-
-function cleanup(done) {
-    async.series([
-        database._clear,
-        database.uninitialize
-    ], done);
-}
-
 describe('System', function () {
-    before(setup);
-    after(cleanup);
+    before(common.setup);
+    after(common.cleanup);
 
     it('can get disks', function (done) {
         system.getDisks(function (error, disks) {