Network-refactor: some clean up of the NetworkService interface
- remove unused public apis
- remove unused members
- change visibility of methods to protected if they do not implement a method in the interface

Signed-off-by: Chiradeep Vittal <chiradeep@apache.org>
Network-refactor: move validateRule to LB manager since it now has access to LB elements.
NetworkServiceImpl does not need a cache of system network offerings
Ensure mocks build to new APIs.

Signed-off-by: Chiradeep Vittal <chiradeep@apache.org>