Fix bug where Workspace page alpha stays 0 in SpringLoaded mode.

The page alpha gets set to 0 by updatePageAlphaValues sometime between
Workspace calling goToState(SPRING_LOADED) and onStartStateTransition.

By the time the transition is over, Workspace is no longer in a modal state
and so alpha never gets restored via updatePageAlphaValues.

Bug: 76449277
Change-Id: I95241395594dd9084763cc3bc51bc55319cadb73