nfs4: remove NfsLoginService interface

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
1 job for master in 1 minute and 19 seconds (queued for 12 seconds)
Status Name Job ID Coverage
  Build
passed build #1281

00:01:19