title: Deinit UITabBarController after presenting new ViewController
body: <p>I have an app in which users can log in. If the user launches the app and is already logged in then the <code>rootViewController</code> is set to my custom <code>UITabBarController</code> but when the user is not logged in the <code>rootViewController</code> is set to LoginVC (View Controller). My problem is that when the user logs out the LoginVC should be presented and the TabBar should be deinitialized. </p>
  
  <p>I have tried:</p>
  
  <pre><code>self.tabBarController?.dismiss(animated: true, completion: {
      self.tabBarController?.present(LoginVC(), animated: true, completion: nil)
  })
  </code></pre>
  
  <p>And things like that... 
  I can present the LoginVC but when I call <code>self.tabBarController?.dismiss</code>
  the LoginVC gets dismissed instead of the TabBarVC</p>
  
  <p>Any help would be greatly appreciated</p>