Comment 26 for bug 1592119

Reviewed: https://review.opencontrail.org/24123
Committed: http://github.org/Juniper/contrail-controller/commit/991fe4a7a1aba74ace881f6471d636146b6aad20
Submitter: Zuul
Branch: R3.0.2.x

commit 991fe4a7a1aba74ace881f6471d636146b6aad20
Author: ashoksingh <email address hidden>
Date: Thu Jun 23 17:20:07 2016 +0530

Add route to trap neighbor advertisement messages to Agent.

Issue:
In case of IPv6 Allowed Address Pair, when switchover happens to new interface,
the traffic does not move to new interface. As part of switchover, Unsolicited
Neighbor Advertisement message from new interface is not trapped to agent.

Fix
Agent now adds a route to trap IPv6 All Nodes Multicast address in each VRF so
that Unsolicited Neighbor Advertisement message reaches agent. Agent, as part
of this message processing updates the Allowed Address pair state machine so
that route preference is updated for new interface and traffic starts flowing
from new interface. Also define separate counters in agent for Solicited and
Unsolicited Neighbor advertisement message.
Also update the UT.

Closes-Bug: #1592119
(cherry picked from commit 6d3008cb1e0fa8bd8316398959785f45e0eef218)

Change-Id: I2363856cb7d1d57e073573140bafc13590031b40