Make sure the hotseat icons are always visible in phone mode

With task bar in unfolded state, we animate from app to home by morphing the task bar into the hotseat. In the folded state, the visibility of the hotseat should never be affected by the task bar state.

Fixes: 309477352
Test: Swipe up from app in folded state with task bar / nav bar unification flag on, make sure that the transition is smooth and the hotseat is always visible. Also make sure unfolded state works as usual.
Change-Id: I1064a0c03e8f7539f8ea4d0322f58be9dff8513e