Avoid conflict surface reset on auto-enter-pip

FullscreenUnfoldController#resetSurface happens in between
RecentsAnimationController cleanup and PipTaskOrganizer#onTaskAppeared
may cause flicker at the end of auto-enter-pip transition.

Fix it by intentionally ignore resetSurface if the task's pinned.

Bug: 203724707
Bug: 204284060
Test: repeatedly swipe to enter PiP from YT on foldables
Change-Id: Ie074e8a506d2526fc081ff4d089a2acb00549286