title: UIAlertController translucency glitch/bug
body: <p>When iOS presents an alert, the translucency is constant. When my app presents one, the alert is white at first, only for half a second, then it becomes translucent. It's a small issue, but it looks messy and alerts should be consistent everywhere I think. Anyways here is the code:</p>
  
  <pre><code>UIAlertController *alertVC = [UIAlertController alertControllerWithTitle:@"Invalid Credentials" message:@"Please try again." preferredStyle:UIAlertControllerStyleAlert];
  UIAlertAction *ok = [UIAlertAction actionWithTitle:@"OK" style:UIAlertActionStyleDefault handler:^(UIAlertAction *action) {
      [_username becomeFirstResponder];
  }];
  [alertVC addAction:ok];
  [self presentViewController:alertVC animated:YES completion:NULL];
  </code></pre>
  
  <p>I'm interested in people's opinions here as well. Is this just too small of an issue for anyone to be concerned about? It looks like this is just the way <code>UIAlertController</code> works (at least when developers use it). Regardless, it looks messy and I would consider it a bug (unless I'm doing something wrong) since it doesn't look the same as when iOS presents an alert, even though it should.</p>