fix(input): input error messages visible on form submit

Added check for parent form `$submitted` attribute.

Notice that `novalidate` attribute should be applied on parent form in order to make it work (Browser preventing submit when not specified)

fixes #5752

src/components/input/input.js

@@ -212,7 +212,7 @@ function inputTextareaDirective($mdUtil, $window, $mdAria) {
     }
 
     var isErrorGetter = containerCtrl.isErrorGetter || function() {
-        return ngModelCtrl.$invalid && ngModelCtrl.$touched;
+        return ngModelCtrl.$invalid && (ngModelCtrl.$touched || ngModelCtrl.$$parentForm.$submitted);
       };
     scope.$watch(isErrorGetter, containerCtrl.setInvalid);