code: public void ValidateCredentialsInGuest(GuestAuthentication auth) throws GuestOperationsFault, InvalidState, TaskInProgress, RuntimeFault, RemoteException {
          getVimService().validateCredentialsInGuest(getMOR(), vm.getMOR(), auth);
      }
docs: * It should have returned a boolean, but...
  Watch out GuestPermissionDenied (subtype of GuestOperationsFault)
  for invalid authentication.