s3:auth: add add_builtin_guests() handling to finalize_local_nt_token()

s3:auth: add add_builtin_guests() handling to finalize_local_nt_token()

We should add Builtin_Guests depending on the current token
not based on 'is_guest'. Even authenticated users can be member
a guest related group and therefore get Builtin_Guests.

Sadly we still need to use 'is_guest' within create_local_nt_token()
as we only have S-1-22-* SIDs there and still need to
add Builtin_Guests.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=13328

Signed-off-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Ralph Boehme <slow@samba.org>