remove mkdirp use

node 10.12 has { recursive: true }

src/test/backups-test.js

@@ -16,7 +16,6 @@ var async = require('async'),
     expect = require('expect.js'),
     fs = require('fs'),
     os = require('os'),
-    mkdirp = require('mkdirp'),
     moment = require('moment'),
     path = require('path'),
     rimraf = require('rimraf'),
@@ -139,7 +138,7 @@ describe('backups', function () {
         const BACKUP_DIR = path.join(os.tmpdir(), 'cloudron-backup-test');
 
         async.series([
-            mkdirp.bind(null, BACKUP_DIR),
+            fs.mkdir.bind(null, BACKUP_DIR, { recursive: true }),
             database.initialize,
             database._clear,
             settings.setBackupConfig.bind(null, {
@@ -371,7 +370,7 @@ describe('backups', function () {
         });
 
         it('succeeds to set backup config', function (done) {
-            mkdirp.sync(backupConfig.backupFolder);
+            fs.mkdirSync(backupConfig.backupFolder, { recursive: true });
 
             settings.setBackupConfig(backupConfig, function (error) {
                 expect(error).to.be(null);