Motivation:
The NfsLoginService aimed to handle RPCSEC_GSS based session and
map GSS context to appropriate Subject. However, this is always
handled by RPC layer (after split of nfs and rpc modules into different
projects). Thus NfsLoginService is simply a dead code.

Modification:
remove NfsLoginService interface

Result:
less dead code

Acked-by: Paul Millar
Acked-by: Lea Morschel
Target: master