ceph-grafana: Set grafana uid/gid on files

ceph-grafana: Set grafana uid/gid on files

We don't need to create a grafana system user (in fact we even don't
set the righ uid to this user) because we're using a container setup.
Instead we just need to be sure to set the owner/group to 472 (grafana
user/group from the container) like we do for ceph/167.
We don't need to set the user/group recursively on /etc/grafana
directory in a dedicated task.
Also on Ubuntu system, the ceph-grafana-dashboards isn't present so on
non containerized deployment we won't have the
/etc/grafana/dashboards/ceph-dashboard directory present (coming with
the package) so we need to be sure it exists.

Signed-off-by: Dimitri Savineau <dsavinea@redhat.com>
(cherry picked from commit 34036c667c244a9a36b8775fb27f5be10fe9fed1)