Common: Avoid duplicate section in ceph.conf
Common: Avoid duplicate section in ceph.conf

See:
 - https://github.com/ceph/ceph-ansible/pull/1018#issuecomment-253491094
 - https://github.com/ceph/ceph-ansible/pull/1018#issuecomment-260276588

The workaround here is rendering `ceph_conf_overrides` before passing it
to `config_template` to be sure we won't have a section added twice in
ceph.conf

Signed-off-by: Guillaume Abrioux <30a9df5a0293a6108675377fa1673f7aa713f915@redhat.com>

font/ceph-ansible,travmi/ceph-ansible,ceph/ceph-ansible,ceph/ceph-ansible,bengland2/ceph-ansible,travmi/ceph-ansible,fgal/ceph-ansible,font/ceph-ansible,bengland2/ceph-ansible,fgal/ceph-ansible,jtaleric/ceph-ansible,jtaleric/ceph-ansible