title: ionic 3 menu does not show up after setRoot
body: <p>In my use case i want to show side menu as well as tabs in my ionic 3 angular app. The use case is: showing tabs initially with side menu hidden (set as enable(false)). The first page shows a button to add to cart, doing this shows a cart in the header area and clicking the cart shows a login page. Once u login the order summary page comes up. At this point i want to show the side menu. So in <code>ionviwedidload</code> i am setting the <code>menu.enable(true)</code>.  Though it shows the menu icon but actual menu does not appear.</p>
  
  <p>The minimal test case is <a href="https://www.dropbox.com/s/tq202w3p6yf32fj/tab-menu_app.zip?dl=0" rel="nofollow noreferrer">https://www.dropbox.com/s/tq202w3p6yf32fj/tab-menu_app.zip?dl=0</a></p>
  
  <p>To Try: <br> <br>
  1. Run the app <br>
  2. Click on the add to cart button <br>
  3. Click on the shopping cart in the header in right side <br>
  4. This brings login page model. click on login button <br>
  5. Summary page shows up with menu icon. clicking it does nothing though <br></p>