WinodowStateAnimator: Remove mD(s|t)d(x|y)

They are always either 1 or 0 and so there is no use. We also fix a bug
in WindowState#getTransformationMatrix where the value should be equal
to mGlobalScale (or at least it was in previous releases).

Bug: 161937501
Test: Existing tests pass
Change-Id: I8ecc88b6be6b4d9b87bc43a1e0319f33b589b46e