title: p-fileUpload does not work more than once primeng
body: <p>I`ll try to explain what it is going on with this component, I have defined the component this way</p>
  
  <pre><code>&lt;p-fileUpload #fileUpload accept=".csv,.txt" maxFileSize="1000000" customUpload="true" (uploadHandler)="uploadFile($event)"&gt;
  </code></pre>
  
  <p>on my package Json I have this
    "primeng": "^4.1.0-rc.3"
  and have this method on the js file</p>
  
  <pre><code> uploadFile(event) {
  
      for (let file of event.files) {
          this.uploadedFiles.push(file);
      }
  
      this.uploadFileService.doSomething(this.uploadedFiles[0]).subscribe(x =&gt; {
          this.fileInfo = x;
          ..do some stuff..
  
      });
  }
  </code></pre>
  
  <p>It works as expected the first time (showing 3 buttons of the component choose, upload and cancel) and letting me choose the file from the popup window and the process continues calling the uploadFile method; the thing is, once it finishes, if I try to upload again the same file it does not allow me to do it.
  It only allows me to choose the file, but the upload button is never enabled and, of course, the uploadFile method is never called. But if I choose another file different from the previous, it works as expected, that means calling the uploadFile method.</p>
  
  <p>I am using</p>
  
  <pre><code>this.fileUpload.clear();
  </code></pre>
  
  <p>just to clear the part where the uploaded file it is showed to the user</p>
  
  <p>Any suggestion?</p>