title: Ionic 2 tab issue
body: <p>I created a page with 3 tabs using ionic 2.Inside one page I created one button and on click of that button I navigate to a new child page by executing
  the push command but whenever I am clicking the tab containing the child page I am not able to see the root page instead I see the new child page.
  I want to see the root page on revisit of the tab page.</p>
  
  <p>Below is my code.. here you can check in about.html i have placed one button to navigate to a child page.Navigation is happening but once I navigate then I am not able to see the about tab page without clicking on back button</p>
  
  <pre><code> tabs.html
      &lt;ion-tabs&gt;
        &lt;ion-tab [root]="tab1Root" tabTitle="Home" tabIcon="home"&gt;&lt;/ion-tab&gt;
        &lt;ion-tab [root]="tab2Root" tabTitle="About" tabIcon="information-circle"&gt;&lt;/ion-tab&gt;
        &lt;ion-tab [root]="tab3Root" tabTitle="Contact" tabIcon="contacts"&gt;&lt;/ion-tab&gt;
      &lt;/ion-tabs&gt;
  
      tabs.ts
      import { Component } from '@angular/core';
      import { HomePage } from '../home/home';
      import { AboutPage } from '../about/about';
      import { ContactPage } from '../contact/contact';
  
      @Component({
        templateUrl: 'tabs.html'
      })
      export class TabsPage {
        // this tells the tabs component which Pages
        // should be each tab's root Page
        tab1Root: any = HomePage;
        tab2Root: any = AboutPage;
        tab3Root: any = ContactPage;
  
        constructor() {
  
        }
      }
  
      abuot.html
      &lt;ion-header&gt;
        &lt;ion-navbar&gt;
          &lt;ion-title&gt;
            About
          &lt;/ion-title&gt;
        &lt;/ion-navbar&gt;
      &lt;/ion-header&gt;
  
      &lt;ion-content padding&gt;
  
      &lt;button ion-button (click)="navigate()" ion-button color="secondary"&gt;GO to LIst&lt;/button&gt;
      &lt;!-- &lt;button [navPush]="listPage" ion-button color="secondary"&gt;Go To About&lt;/button&gt; --&gt;
          &lt;!-- &lt;button ion-button color="secondary"&gt;Secondary&lt;/button&gt; --&gt;
      &lt;/ion-content&gt;
  
      about.ts
      import { Component } from '@angular/core';
      import {ListPage} from '../list/list';
  
      import {ViewController, NavController} from 'ionic-angular';
  
      @Component({
        selector: 'page-about',
        templateUrl: 'about.html'
      })
      export class AboutPage {
  
  
        constructor(public navCtrl: NavController,public viewctr: ViewController) {
        }
        navigate(){
           this.navCtrl.push(ListPage);
        }
  
      }
  </code></pre>