Send shutdown callback only during animation destruction

The shutdown callback is currently used only by audioplay.cpp to destroy the audio player.
Sending shutdown when the animation is destructed makes sure the audio
player is not being destroyed before its boot animation part is being displayed.

Test: Modified bootanimation, sound in second last part of bootanimation
plays
Bug: 157407957

Change-Id: I47f57643791e73e4a4fa1597309dccb1f52f2316