Set TvPipController's state only when PiP finished appearing

When asking PipTaskOrganizer to animate the PiP to a different position
while it's still in the appearing transition, the PiP could get stuck in
a bad state where the PiP contents and menu items weren't drawn.
This change avoids this by only calling #scheduleAnimateResizePip once
the PiP has finished appearing.

Test: manual
Bug: 220110011
Change-Id: Ie62adea6f2cb5a4abdd6c4b8f9ff23c040077046