NetworkService: Renamed cur_service_id_name -> current_name.

Also introduced accessor for current_name into public API to make
current_name read-only..

Renamed internal function get_net_service_name -> get_new_name
NetworkService: removed EnableDisable function

Reasons for removal:
- it worked for netconfig only
- it only Enabled the service
- it was replaced by more generic function EnableDisableNow
Code cleanup
Updated spec
Rspec smoke test for NetworkService