Configure CRUSH map appropriately on AIO Ceph

Introduce a parameter which can be used to set up the CRUSH map
optimally in single-node Ceph installations. This allows AIO Ceph
installs to report HEALTH_OK.

Closes-Bug: 1340168
Merge pull request #18 from CiscoSystems/bugs/1340168

Configure CRUSH map appropriately on AIO Ceph