title: Handle tab change on when having multiple MatTabGroup
body: <p>To be able to enable/disable some email templates I've divided my select-tabs into different groups. </p>
  
  <p>Please see stackblitz: <a href="https://stackblitz.com/edit/angular-ddysaa" rel="nofollow noreferrer">https://stackblitz.com/edit/angular-ddysaa</a> </p>
  
  <p>Initially, all tabs are set to index 0. If I first go to <strong>index 3 in group 1</strong>, then <strong>index 2 in group 2</strong>, then back to <strong>index 3 in Group 1</strong>, the selectedTabChange-handler isn't triggered. </p>
  
  <p>The cause for this is that when I go back to group 1 and visit index 3 <strong>again</strong> this isn't read as a tabChange, of course. </p>
  
  <p>I've tried to handle this by resetting each groups' <code>selectedIndex</code> to 0 every time there's a group change, but this doesn't work. I can't understand why this doesn't work. </p>
  
  <p>Is this the correct workaround for doing this? If so - what am I missing? 
  Is there any other way to handle template groups to get the same behavior? </p>