Fix weird split-screen secondary task animation

As CL[1] corrects the screenBounds of remote animation target,
and we are now using RemoteAnimationTarget#localBounds to offect the
position.

Remove the offset logics in AppWindowAnimationHelper#updateSourceStack,
and TaskViewSimulator#setPreview, then refine computeSurfaceParams
with offseting the position of HOME task by localBounds.

[1]: I793f01fb290fe65af1bbf8e29e429fbca63ac255

Fix: 153581126
Test: manual as below steps:
     1) Launch a app, swipe up to overview screen.
     2) Tap app icon and pressing "Split screen" item.
     3) After entered split-screen mode, taps the task view.
     4) Make sure the secondary task animation the movement is
        correct and smoothly.

Change-Id: I0e4ed1465e80f48336908813ac694fb3aaa3c347