floatPlaceholder="never" doesn't work on input with [mdAutocomplete]

http://plnkr.co/edit/Nn20g78t1NXrMCFI9ABL?p=preview

https://github.com/angular/material2/blob/master/src/lib/autocomplete/autocomplete-trigger.ts#L147 / https://github.com/angular/material2/blob/master/src/lib/autocomplete/autocomplete-trigger.ts#L137 this is likely the reason

@kara 