`ceph-docker-common`:
  At the moment there is a lot of duplicated tasks in each
  `./roles/ceph-<role>/tasks/docker/main.yml` that could be refactored in
  `./roles/ceph-docker-common/tasks/main.yml`.

`*_containerized_deployment` variables:
  All `*_containerized_deployment` have been refactored to a single
  variable `containerized_deployment`

duplicate `cephx` variables in `group_vars/* have been removed.

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