title: Angular 2 async validator always invalid
body: <p>I have the following form control with the simplest async validator I could write:</p>
  
  <pre class="lang-js prettyprint-override"><code>this.aliasCtrl = this._fb.control('', [(control: AbstractControl) =&gt; {
    return new Promise(resolve =&gt; {
      console.log(this.aliasCtrl);
      resolve(null);
    });
  }]);
  </code></pre>
  
  <p>My form definition is:</p>
  
  <pre class="lang-js prettyprint-override"><code>this.contactForm = this._fb.group({
    alias: this.aliasCtrl
  });
  </code></pre>
  
  <p>My form control is always invalid. 
  Here's a plunker: <a href="http://plnkr.co/edit/vyr48ke7fWEUwrXy43tn?p=preview" rel="nofollow noreferrer">http://plnkr.co/edit/vyr48ke7fWEUwrXy43tn?p=preview</a>
  I'm sure I've miss something but I cannot find what.</p>
  
  <p>Thanks for help.</p>