s3:client: The smbspool krb5 wrapper needs negotiate for authentication

s3:client: The smbspool krb5 wrapper needs negotiate for authentication

If you create a new printer it doesn't have AuthInfoRequired set and so
cups calls the backend with:

  AUTH_INFO_REQUIRED=none

In this case we need to return:

  ATTR: auth-info-required=negotiate

and return an error that we require authentication.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=12886

Signed-off-by: Andreas Schneider <asn@samba.org>
Reviewed-by: Jeremy Allison <jra@samba.org>
Autobuild-User(master): Jeremy Allison <jra@samba.org>
Autobuild-Date(master): Sat Jul 15 06:43:47 CEST 2017 on sn-devel-144