Fix two issues with splitting from Taskbar

This patch fixes two issues that would arise when the user initiated split from Taskbar:
1) The Overview Actions View would animate out, then erroneously pop back in.
2) When initiating split from home repeatedly, the task thumbnail grid would not animate downward properly, instead staying in the wrong y-position.

Both issues were caused by the fact that we now have a new way to enter OverviewSplitSelect (directly from Taskbar/Home), which rendered some of our old assumptions incorrect. Namely:
1) When we finish transitioning to OverviewSplitSelect, we need to update OverviewActionsView visibility so that it stays hidden.
2) mSplitHiddenTaskView is no longer a good way to tell if we are in split select state or not.

Fixed by adding a new call to updateCurrentTaskActionsVisibility() to the end of the split staging animation, and by making sure translations get reset every time resetFromSplitSelect() is called.

Fixes: 271624078
Fixes: 261544937
Test: Manual, verified on large and small tablet screens with various types of split invocations and rotation combinations.

Change-Id: Ied0f4818ce6da599845ccd07e9dc96ef4ba030c3