Expansion panel in tab shows its content in collapsed state when tab become active

[ipassynk]

Bug, feature request, or proposal:

bug

What is the expected behavior?

content should be collapsed

What is the current behavior?

Expansion panel in tab shows its content in collapsed state when tab become active

What are the steps to reproduce?

1. Have a tabs and each tab has an expansion panel.
2. The first active tab shows the expansion panel correctly - collapsed state
3. Click on the second tab
4. Observe that the expended panel in the tab shows the content (it is not hidden)

https://stackblitz.com/edit/angular-material2-issue-vqp5mt

<mat-tab-group>
	<mat-tab label="1">

		<mat-expansion-panel>
			<mat-expansion-panel-header>
				header1
			</mat-expansion-panel-header>
			content1
		</mat-expansion-panel>

	</mat-tab>


	<mat-tab label="2">

		<mat-expansion-panel>
			<mat-expansion-panel-header>
				header2
			</mat-expansion-panel-header>
			content2
		</mat-expansion-panel>

	</mat-tab>
</mat-tab-group>

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?

[josephperrott]

Duplicate of #5269

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