Autocomplete sets itself back to $pristine state after input

[plamenlazarov]

While typing, autocomplete input element switches between ng-dirty and ng-pristine classes.

Please refer to the following demo page: http://demos.telerik.com/kendo-ui/autocomplete/angular

Steps to reproduce:

1.  Inspect the autocomplete input element on initial page load.
2. Type into the autocomplete field.
3. The input's state switches between ng-dirty and ng-pristine.

Reported in ticket ID 935978