Forced to max one offsetAnimationJob in progress

Previously, it was possible for a new job to start before the previous
one was canceled. This could lead to an inconsistent state because some
properties are initialized at the start of a job and reset when it ends.

To avoid this, the new job is now required to wait for the previous job
to finish before it can start. This ensures that all properties are in a
 consistent state before the new job begins.

Test: mp :SystemUIComposeGallery
Bug: 291025415
Change-Id: I6d3b0cc00df13da25c711e42e713f4b13e4611b9