md-not-found doesn't work if there is a ng-if on the md-autocomplete

[ramprabhuj]

There is some caching behavior on the MDAutoComplete controller which assumes the element() object will be the same in the lifecycle. This makes the check for ctrl.hasNotFound being reported as undefined. seems like this check should be done with no caching in the link() function and not in the template() function.

http://codepen.io/anon/pen/GoYKOb

[devversion]

Introduced in 655eb0f. This would work properly when element isn't hidden at compilation cycle. So created a PR, which tests this issue and created a accompanying fix for that issue. But I'm not sure using an attribute is prefered, but I thought this will be also good for the user to keep that attribute. Need feedback.