Netvirt classifier should better use the Genius InterfaceManager

Instead of calling the Genius RPCs, the InterfaceManager should be better taken advantage of in the GeniusProvider. This will allow for less code duplication and will be less error-prone.

More specifically, at least the following should be used from the InterfaceManager:
getNodeConnectorIdFromInterface()
getNodeIdFromDpnId() // or the equivalent.