Fix garbage deref with DisplayList property structures

This is the real fix to issue 6158892. We currently delete
transform/camera structures at DisplayList destructor time, if these
structures are not NULL. We set the fields to NULL in an init() method
called (eventually) by the constructor. But it is possible for the object
to be destroyed before that init code is called, resulting in the deref
bug reported. The fi is to set these structures to NULL directly in the
constructor.

Issue 6158892i: Device runtime restarts frequently

Change-Id: Ibfa0f9314767eed6fd51f4ec7edc0d0edd5fdd0f