Update notes for submitted changes

* - There are two paths in the vrouter code where interfaces (OS visible interfaces - netdev to be specific) are manipulated. One is in the call chain to process agent request and the other is when the interface is deleted by linux (for e.g.: a pseudo or a tap interface going away resulting in the notifier call chain). In the latter path, netlink lock is acquired by the notifier chain, whereas in the former path there is no netlink lock.