Fix predictive back be canceled due to moveTaskToFront transition.

In multi-window mode, tap on a on-screen task could trigger a TO_FRONT
transition which intent to move it to front. It shouldn't cancel
predictive-back animation since the transition won't really have any
visibility state change.

Bug: 321923516
Test: enter split screen, open a sub-activity in task A, tap on
another task B, then trigger predictive back on task A, verify
the predictive back won't be canceled from TO_FRONT transition.

Change-Id: I3b0b5153cf6ceb07d9f3d8fa5fc289741c2a8e54