Do nothing when a finishing Activity configuration changed

Primary Activity and secondary Activity were both finished
while starting another Activity with FLAG_ACTIVITY_CLEAR_TASK
flag. The secondary container was then removed and the primary
container was resized to fullscreen while the organizer gets
the secondary TaskFragment info-changed event. And the primary
container was removed by primary TaskFragment info-changed event
afterward.

Since the primary Activity was resized before completely being
destroyed. The organizer got an onActivityConfigurationChanged c
allback and resulted in another placeholder activity being launched.

Bug: 236272623
Test: making Duo calls
Change-Id: I851828f739a4937725510d99cbdfae9ed212a023