Fix stopping activity when removed from waiting visible

During refactoring in ag/613666 waitingVisible flag clearing
was mistakenly removed. It was added back in ag/1221328 but
only for activities that are finishing.
This caused activity not being stopped in some cases when
window visibility change was handled before receiving idle
callback from client. This is easily reproducible when there
is a scene transition animation specified.

Bug: 31078584
Change-Id: Ic09c5199ad4fceae0607e4bcce02be5335c8870b