title: Radio buttons in Angular2 Model Driven forms not working as expected
body: <p>If I create radio buttons in my model driven form, they work fine but they don't have the radio button selected reflected by the formControlName default value.  For example: </p>
  
  <pre><code>&lt;input type="radio" formControlName="isPublic" name="isPublic" value="false" id="keepPrivate" &gt;&lt;label for="keepPrivate"&gt;Keep it Private&lt;/label&gt;
  &lt;input type="radio" formControlName="isPublic" name="isPublic" value="true" id="makePublic" &gt;&lt;label for="makePublic"&gt;Make it Public&lt;/label&gt;
  {{form.value.isPublic}}
  </code></pre>
  
  <p>If I have this it works correctly, but I can see the value of <code>form.value.isPublic</code> is false (as output in the last line to confirm) and yet no radio button is selected by default.</p>
  
  <p>I tried to correct this by adding <code>[checked]</code> to each to drive the default value.  This works for the page load, in that defaults are properly selected in the radio buttons.  It even works for ONE selection - in that I can select the other radio button, it will be selected, the first one will be unselected, and the <code>{{form.value.isPublic}}</code> will change from <code>false</code> to <code>true</code>.  </p>
  
  <pre><code>&lt;input type="radio" formControlName="isPublic" [checked]="!form.value.isPublic" name="isPublic" value="false" id="keepPrivate" &gt;&lt;label for="keepPrivate"&gt;Keep it Private&lt;/label&gt;
  &lt;input type="radio" formControlName="isPublic" [checked]="form.value.isPublic" name="isPublic" value="true" id="makePublic" &gt;&lt;label for="makePublic"&gt;Make it Public&lt;/label&gt;
  {{form.value.isPublic}}
  </code></pre>
  
  <p>The problem comes when I select the first radio button again - on the first click the radio button selection state doesn't change at all, but the <code>{{form.value.isPublic}}</code> output changes back to false.  If I click it again, then the radio button selection state changes.  So it takes two clicks to switch it back to the default.  If I click the other one again after that, it changes as expected but switching back to the first one takes two clicks (one click updates the form value and the second click changes the selection state of the radio button).</p>
  
  <p>What should I be doing in this situation to have the radio buttons function correctly and reflect the default value for the form?</p>