perf(input): prevent multiple $digest when input is blurred

@kevinjamesus86 noticed that the input control would trigger a $digest
cycle every time it was blurred, https://github.com/angular/angular.js/commit/adcc5a00bf582d2b291c18e99093bb0854f7217c#commitcomment-7129512.

After the control is in a $touched state, other $digest cycles are
unnecesary.

References #7673
The recommended way to execute an expression in Angular from outside angular realm (DOM events) is to use [`scope.$apply`](https://docs.angularjs.org/guide/scope#scope-characteristics). 

The error in your directive comes from [line 244](https://github.com/angular-ui/ui-select/blob/master/dist/select.js#L244) when the `close` method, which is executed inside the angular realm (a $digest cycle), calls a DOM method (`focus()`). Any other directive that binds to the `focus` DOM event and attempts to execute an expression in the angular realm using $apply will cause an `$apply already in progress` exception.