title: angular material md-autocomplete remove md-floating-label attribute not working
body: <p>I have the following code when using the md-autocomplete directive in angular-material. I want to remove the md-floating-label entirely from the element if the acType != FORMULA:</p>
  
  <p>html:</p>
  
  <p><code>ng-attr-md-floating-label="{{ autocompleteFloatingLabel }}"</code></p>
  
  <p>JS:</p>
  
  <pre><code>scope.autocompleteFloatingLabel = false;
  if (scope.acType == Constants.Autocomplete.FORMULA) {
    scope.autocompleteFloatingLabel = 'Add a formula here ';
  }
  </code></pre>
  
  <p>I have tried setting the autocompleteFloatingLabel to undefined instead of false I have also tried remove the brackets in the HTML template. Nothing seems to work. I know that the scope.acType is evaluating to the proper value, but md-floating-label seems to still be there when it shouldn't be.</p>