Add post-install script to populate Ceph

[epuertat]

Default Ceph install ends up with a very basic setup, so we should populate it with more complex settings:

• RBD pool
• RBD Images, snapshots
• Add data to RBD Images.
• More RBD pools?
• More RGW daemons?
• More RGW buckets
• More RGW users?
• Add objects to RGW buckets?

Additionally, we should decide if it's interesting to configure the following features:

• Config RBD-mirroring?
• Config iSCSI?
• Config NFS?