Support directional-dpls & cleanup sfc-translator

Support directional-dpls & cleanup sfc-translator

This patch adds support for the new directional-dpl sfc spec. It allows
to setup both the egress and ingress ports of a port pair as distinct
service funcion data plane locators so that they are used appropriately
depending on the direction of a symmetric path.

This patch also fully transitions to the logical sff configuration model
cleaning up code that applied to the old configuration model. The
logical sff configuration model makes thing much simpler: neutron port
uuids are configured directly in sfc as logical interface data plane
locators without the need to fetch aditional data about them.

Change-Id: Ibee6e2707878932ae1efbfd4ab0eae8a78056437
Signed-off-by: Jaime Caamaño Ruiz <jcaamano@suse.com>