title: UINavigationController push view and show toolbar has strange toolbar animation
body: <p>I have a  <code>UINavigationController</code> which is inside of a <code>UITabBarController</code>.  In my nav controller, I want to show the <code>toolbar</code> when I push a view, effectively hiding the tab bar at the same time.  It "works", but the toolbar animates up from the bottom, rather than doing a smooth slide in transition.</p>
  
  <p>Added to my first view:</p>
  
  <pre><code>- (void) viewWillAppear:(BOOL)animated
  {
      [self.navigationController setToolbarHidden:YES animated:animated];
      [super viewWillAppear:animated];
  }
  
  - (void) viewWillDisappear:(BOOL)animated {
  
      [self.navigationController setToolbarHidden:NO animated:animated];
      [super viewWillDisappear:animated];
  }
  </code></pre>
  
  <p>Why is the <code>toolbar</code> animating up from the bottom?  Shouldn't it slide in so the transition between sliding out the <code>tabbar</code> and in with the <code>toolbar</code> can be seemless?</p>