Encapsulate some port properties in the PortContext

Bindings to host or status may need further encapsulation
to avoid exposing mechanism drivers to underlying DB model
details. This was particularly true in the case of the
l2pop mech driver.

Partially-implements: blueprint neutron-ovs-dvr
Supports blueprint: ml2-hierarchical-port-binding

Change-Id: If2a373ef04d19b164585fb4bde4fe6e0cfaf43be
ML2 additions to support DVR

This patch introduces the changes necessary to
support DVR at Layer 2 with ML2, and L2pop.

Partially-implements: blueprint neutron-ovs-dvr

Change-Id: I709d877e7df83728868e68e023e6a37bb2e11704
Add L3 Scheduler Changes for Distributed Routers

This patch implements the L3 Scheduler changes for the
Distributed Virtual Routers.

Partially-implements: blueprint neutron-ovs-dvr

Change-Id: I407c3d639ebdf885b1418bceac7cfc251e7eba1f
Co-Authored-By: Carl Baldwin <carl.baldwin@hp.com>
Co-Authored-By: Armando Migliaccio <armamig@gmail.com>
Merge DVR patches together