Update activity visibility for all users

The visibility of the activities of a background user was not
updated because the #topRunningActivity only returns the top
activity that can be shown to the current user.

This issue should have existed since commit 232ec86d.

Bug: 217271185
Test: Switch user while having activity embedded
Test: Start embedded activities and back
Test: atest ActivityRecordTests
Change-Id: Ia89e39a0ce7e569a820a2b5637a70597861e9666