Bug: Datepicker value change event fires when changing min value of it

Bug, feature request, or proposal:

Bug

What is the expected behavior?

I am not sure it is expected to behave like that or not, but I think that changing min value of datepicker shouldn't fire value changes event of the form group. I changed value of min date inside subscribe method because I want to have mindate dynamically updated. I checked two conditions one with the formgroup where it happens twice all the time and another condition using just formcontrol this issue happens only first time.
If I comment out the update of the mindate inside subscribe everything will be okay

What is the current behavior?

Form Group value change happens when changing Datepicker min value via two way binding, Min value update happens inside Subscribe method. This issue causes to fire valuechanges twice

What are the steps to reproduce?

Reproduction is StackBlitz using the formgroup
https://stackblitz.com/edit/datepicker-min-date-bug?file=app/datepicker-min-max-example.ts

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

I think something is odd because different conditions behave differently ( for example as I stated above about formcontrol vs formgroup)

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

Angular Material 5.0.0-rc3

Issue にリンクされている StackBlitz の再現を、app/datepicker-min-max-example.ts とその form-group および form-control のケースから実行します。subscription 内で datepicker の min 値を更新したときの value-change の emission を比較します。動作に一貫性があり、意図しない重複した emission が発生しなくなれば完了です。