Fix leak in TransitionInflater

A static map in TransitionInflater keyed off of Context instances,
which could cause contexts/activities to leak over time. This
fix removes that map and simply creates a new inflater each time.
The savings of the cached inflater was minimal an unnecessary, and the
intended sharing is in the context embedded in the inflater anyway.

Issue #11436919 leak in TransitionInflator

Change-Id: Ic05ca47f57723bd572bb6143df4035d66eedf5ad