Fix index out of bounds when removing deferred containers

This makes the commit 793442c5 general to handle the removal from
all level since the hierarchy won't always keep the same shape.

Also rename to handleCompleteDeferredRemoval since it is not a
pure function for checking.

Bug: 159865315
Test: atest WindowContainerTests#testHandleCompleteDeferredRemoval

Change-Id: I34e02652fb765c1cf78cbd3e86a07e592f02e7df