Allocate buffers locally in systems without SurfaceFlinger

In Brillo systems, we have no applications and configure
SELinux policy statically.  In this model, we do not need
a special service to allocate buffers, since any process
that needs buffers can be appropriately marked at build time.

Bug: 26936651
Test: A test program on brilloemulator can allocate buffers for
      the camera with this patch.

Change-Id: Ifcdb7a4b878f9a26f4899c7b75a12447dcdb0ac9