L2 Model additions to support DVR

This patch introduces the models, the DB migrations
and the config options required by the L2 layer to
support DVR east/west traffic.

These changes will be used by the control-plane made
of ML2, L2pop and L2 agent.

Two new configuration options have been introduced:
'dvr_base_mac' is used to set DVR MAC addresses apart
from tenant ones (every distributed router will have
ports being created on compute hosts) and
'enable_distributed_routing' is used to enable dvr
support in the L2 agent. This gives the capability of
rolling out the dvr functionality in stages.

Partially-implements: blueprint neutron-ovs-dvr

DocImpact

Change-Id: Iab6505f239d2c4c9bcbf4e32a292d7b4b5320c8e
Authored-by: Vivekanandan Narasimhan <vivekanandan.narasimhan@hp.com>
Co-Authored-By: Armando Migliaccio <armamig@gmail.com>
RPC additions to support DVR

This patch introduces the RPC contract changes
required for both the server (plugin) and agent
to propagate and retrieve additional information
about Distributed Routers, like MAC addresses
and Port Bindings.

Partially-implements: blueprint neutron-ovs-dvr

Change-Id: I04a2ee5fceea79d2786c799178f8dd1675925a39
Authored-by: Vivekanandan Narasimhan <vivekanandan.narasimhan@hp.com>
Co-Authored-By: Armando Migliaccio <armamig@gmail.com>
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