nfs: set idmap config for Ceph-NFS

nfs: set idmap config for Ceph-NFS

Currently NFS Ganesha (ceph-nfs) consumes /etc/idmapd.conf, which
controls mapping of user/owner identities under NFSv4+. With
containerized service deployment, this file is an immutable part of the
container image and cannot be modified.

Here we provide group variables, and a taskk and templates for the
ceph-nfs role, to set the path of the idmap configuration file and
to make the most common adjustment to the contents of that file --
namely to set the 'Domain'. We default the path to /etc/ganesha/idmap.conf
so that we will not conflict with /etc/idmapd.conf on the controller nodes
where ganesha runs. NFSv4 clients, as used for example by the Cinder NFS
driver, consume /etc/idmapd.conf and may require different settings than
what is wanted for NFS Ganesha. Additionally, because we already bind
/etc/ganesha from the host into the ceph-nfs container, the file NFS
Ganesha consumes will no longer be an immutable part of the container.

Closes: https://bugzilla.redhat.com/show_bug.cgi?id=1925646
Signed-off-by: Tom Barron tpb@dyncloud.net
Co-Authored-by: Guillaume Abrioux <gabrioux@redhat.com>