Add maintenance playbook

This playbook was made to automate Ceph servers maintenance
Typical use case: hardware change
By running this playbook you will set the 'noout' flag on your
cluster, which means that OSD **can't** be marked as out
of the CRUSH map, but they will be marked as down.
Basically we tell the cluster to don't move any data since
the operation won't last for too long.

Signed-off-by: Sébastien Han <sebastien.han@enovance.com>
Merge pull request #66 from leseb/wip-maintenance

Add maintenance playbook