Fix#1: L2 multicast route not getting deleted.
When VRF delete is issued, agent unsubscribes from VRF and issues a walk to
clear all externally(BGP peer) created paths to be deleted. For L2 multicast
fabric tree path, the peer is MULTICAST_TREE_BUILDER. This was not getting
deleted. So multicast route used to retain the same resulting in VRF not getting
deleted. Previous to EVPN code it used to work as multicast route had only one
path and on VRF delete it used to be flushed, however EVPN brings in path in
multicast route for every composite NH created for replication.

Fix#2: Parsing of ethernet tag and mac address in retract message
Reference
https://github.com/manishsing/contrail-controller/commit/5d097d9000de0c91bdbad67c8bb52db061e3f0a8

Change-Id: I97583ebefdcf647276b13fdd70893709ccba7fc9
Closes-Bug: 1386924