Fix divider not updated when moving split-tasks from fold -> unfold

As starting unfold transition animation that the running split-tasks may
not yet visible and the transition type could possible be
TRSANSIT_TO_FRONT instead of TRANSIT_CHANGE depends on the user
unfolding speed and the display power state, which leads to the
SplitTaskUnfoldAnimator could not receive onTaskAppeared to update
divider surface by wrong transition type and isApplicableTask check in
UnfoldTransitionHandler.

Ensure SplitTaskUnfoldAnimator receives onTaskAppeared when unfolding
the device during starting unfold transition through
UnfoldTransitionHandler#startAnimation with the right logic check.

Fix: 278045290
Test: manual as following scenarios:
  A) Disable auto-rotate on folded screen
    1. Enter split-screen on folded screen in portrait.
    2. Unfolded the screen
    3. Expect not seeing the divider gone.

  B) Enable auto-rotate on folded screen
    1. enber split-screen on folded screen in landscape.
    2. unfolded the screen.
    3. Expect not seeing the divider being miss-placed on
       top or on left hand side.

Change-Id: I08f737257f1cbc84f08ec4036ed561017b99f67a