mariux-6.1.7-446

Currently, operations which send uid or gid attributes (e.g. chgrp) try
to use idmap which results warnings like "Request-key: Cannot find
command to construct key 322998654" in the syslog, because we don't have
id_resolver configured in /etc/requesst-key.conf.

When the idmap operation fails, the uid of gid are send numerical, so
there is no problem aside from the log message.

Allow idmapping to be disabled for RPC_AITH_MARIUX just as for
RPC_AUTH_UNIX.