Ensure the tmp dir exists on in-process re-runs issue caught in [#4963]

Work around for: joliss/node-quick-temp#8

lib/commands/test.js

@@ -7,6 +7,7 @@ var SilentError = require('silent-error');
 var path        = require('path');
 var win         = require('../utilities/windows-admin');
 var existsSync  = require('exists-sync');
+var mkdirp      = require('mkdirp');
 
 var defaultPort = 7357;
 
@@ -44,6 +45,8 @@ module.exports = Command.extend({
   },
 
   tmp: function() {
+    // workaround for: https://github.com/joliss/node-quick-temp/issues/8<Paste>
+    mkdirp('tmp');
     return this.quickTemp.makeOrRemake(this, '-testsDist');
   },