Teach Control Node to handle change in VN index

Following changes are implemented:

- OriginVn is no longer stored in the primary XMPP route
- OriginVn is added to secondary routes during replication
- Change in VN index triggers notification of all routes in the RI
- Replicator updates the OriginVn for secondary routes
- Virtual Network for primary routes in a VRF is obtained from RI

Change-Id: I987431be6970ecba35485317648af2624b01ad53