Fix a GraphicBuffer leak in SurfaceTexture

This leak was intentional, it was there to deal with the fact that
some gralloc implementations don't track buffer handles with
file-descriptors so buffers needed to stay alive until there were
registered, which is not guaranteed by binder transactions.

In this new implementation, we use a small BBinder holding a
reference to the buffer, which with tuck into the parcel. This forces
the reference to stay alive until the parcel is destroyed, which
is guaranteed (by construction) to happen after the buffer is
registered.

this allows the public facing API to not expose the previous hack.

Change-Id: I1dd6cd83679a2b7457ad628169e2851acc027143