Fix broken Create multiple VPNs tests

Fix broken Create multiple VPNs tests

Deletion of bgpvpn with router associations should move vpn-interfaces to router

On deletion of bgpvpn with router associations, vpn-interfaces under
that bgpvpn will get updated with router as its vpn-instance name.
This will trigger remove and add of vpn-interface logic.
At present, former happens but latter does not.

Since, vpn-interace operational data is moved from operational
vpn-interface object to vpn-interface-op-data keyed on rd, interface name
vpn-interface remove/add can proceed without inter-dependency.

This fix removed batched processing of vpn-interfaces in swap scenarios
and does remove and add then and there in update event handling.

Partial-Bug: NETVIRT-1106
Change-Id: Id2b4b07e6c99fb3b5ecdc0f6063fdbd8a854e415
Signed-off-by: Deepthi V V <deepthi.v.v@ericsson.com>