Do not reset surface when entering PiP

When UnfoldAnimationController is present and entering PiP from a Task
with multiple activities, the resetTask within UnfoldAnimationController
could conflict with the PiP animation and cause flicker.

Fixed this by ignoring restTask in UnfoldAnimationController if there is
no state change going on.

Bug: 261996076
Test: Enter PiP from Task with multi-Activity on foldables
Change-Id: I7f13e86d030d427383e65a37efde13ec94dea2a8