no quota for allowed address pair

There is no quota for allowed address pair. User can create unlimited
allowed address pairs. I add quota for allowed address pairs.

Change-Id: I2efb0c0f527f1fb22c4d4b07f6d280863f565648
Closes-Bug: #1336207
Merge "no quota for allowed address pair"
Merge "RPC additions to support DVR"
Modify L3 Agent for Distributed Routers

This patch is an enhancement to the existing L3 Agent.
This allows the L3 Agent to support distributed routers
by enhancing the router object to function across
multiple nodes.

Utilized two new types of namespaces:

- FIP to handle multiple VM fips and routers per node
- SNAT to handle centralized SNAT per router

Rules and tables are enhanced and added to support routing
across distributed routers without going to a centralized
router.

Finally, a new configuration param 'agent_mode' is introduced
and it controls what the L3 agent can do: the available values
are: 'legacy', 'dvr', 'dvr_snat' (more details inline).

The l3-scheduler uses the newly introduced agent_mode to
determine what L3 agent to select during the scheduling
process.

Partially-Implements: blueprint neutron-ovs-dvr

DocImpact

Change-Id: Icead821bb74372b15aac2e5cefe8ad7f08c037ab
Co-Authored-By: Rajeev Grover <rajeev.grover@hp.com>
Merge DVR patches together