mat-accordion cause closed event to fire on already closed mat-expansion-panel

[wootapa]

Bug, feature request, or proposal:

Expanding a mat-expansion-panel inside an mat-accordion will cause its sibling mat-expansion-panel's to fire the closed event. This happens only on the first expansion.

What is the expected behavior?

Closed event should not fire on already closed mat-expansion-panel.

What is the current behavior?

On first expansion, the closed event is fired on all mat-expansion-panel's except the one you clicked.

What are the steps to reproduce?

https://stackblitz.com/edit/angular-e4egwm

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

Material 5.0.2 and Angular 5.00

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