MatStepper treats steps as `interacted` if you immediately return to a previous step

#### Bug, feature request, or proposal:

Bug

#### What is the expected behavior?

Angular-material forms should be presented in a non-error state when the conditions of the default ErrorStateMatcher are not met (not touched or not submitted)

#### What is the current behavior?

When a form is presented inside a mat-stepper, when traversing to a previous step, the form will be in an error state even if the form is pristine and un-submitted. Any attempt to try to reset the form or FormGroupDirective fails.

#### What are the steps to reproduce?

https://stackblitz.com/edit/angular-material2-issue-fay224

#### What is the use-case or motivation for changing an existing behavior?

#### Which versions of Angular, Material, OS, TypeScript, browsers are affected?

#### Is there anything else we should know?

Comienza con la reproducción enlazada de StackBlitz y sigue la interacción de MatStepper con el formulario y el ErrorStateMatcher predeterminado al volver a un paso anterior. Se considera terminado cuando un formulario sin cambios y no enviado sigue sin errores al volver a visitar un paso, y cuando restablecer el formulario o FormGroupDirective funciona como se espera.

Escrito por el modelo de indexación a partir del texto del issue.