The NFS-Admin API has been added to go-ceph v0.15.0. As the API can not
be tested in the go-ceph CI, it requires build-tag `ceph_ci_untested`.
This additional build-tag has been added to the `Makefile` and should be
removed when the API does not require the build-tag anymore.
See-also: ceph/go-ceph#655
Signed-off-by: Niels de Vos <ndevos@redhat.com>
