Part-1 of EVPN enhancements to support IPv6

1. Change route for EVPN route to be <MAC + IP-Address>
2. Add EVPN routes for IPv4 and IPv6 addresses for local VMs
3. Support EVPN route addition from control-node
4. Remove duplicate constructors for Layer2RouteKey
5. Modify UT code accordingly

Change-Id: I6a9c1ac70feec95aa8ac5563e16a853811082fd9
Merge "Part-1 of EVPN enhancements to support IPv6"