Fix animation target rule due to split screen arch change

Because singleTop root arch change, it makes animation target as
only one rather then both split root as target. It cause some
expection callback wrong for client such as shell split side and
Launcher side.
We should change animation target rule to follow previous behavior
before singleTop change.

Fix: 228572519
Test: manual
Test: pass existing tests
Change-Id: Id68cb0ae22ed39ad42d0593bf152f5bd3bd5f9f1