remove mkdirp use

node 10.12 has { recursive: true }

src/apptask.js

@@ -37,7 +37,6 @@ var addons = require('./addons.js'),
     eventlog = require('./eventlog.js'),
     fs = require('fs'),
     manifestFormat = require('cloudron-manifestformat'),
-    mkdirp = require('mkdirp'),
     net = require('net'),
     os = require('os'),
     path = require('path'),
@@ -176,7 +175,7 @@ function createAppDir(app, callback) {
     assert.strictEqual(typeof callback, 'function');
 
     const appDir = path.join(paths.APPS_DATA_DIR, app.id);
-    mkdirp(appDir, function (error) {
+    fs.mkdir(appDir, { recursive: true }, function (error) {
         if (error) return callback(new BoxError(BoxError.FS_ERROR, `Error creating directory: ${error.message}`, { appDir }));
 
         callback(null);