TripleO should allow discovery of Ceph OSD devices based on device descriptions

At a large scale, it may be difficult to specify Ceph OSDs, and their journals, by device name without first automating the generation of the yaml that is provided as input to TripleO. This is a proposal to move the burden of generating this type of input yaml from the deployer to the deployment tool.

In a small deployment, with uniform storage nodes, the deployer may specify a list of OSD devices, e.g. ['/dev/sdb', '/dev/sdc', '/dev/sdd']. However, at large scale, the number and type of devices may differ due to purchasing hardware at different times. This complexity may be compounded if the hardware device names are not stable across reboots. Though these matters may be resolved by using node-specific hiera data and using a path like /dev/disk/by-path/ with PCI IDs, e.g. pci-0000:02:00.0-scsi-0:0:0:0, the deployer would need to retrieve this data from Ironic and generate the THT yaml using a scripting language. An alternative to this solution, is to be able to use a higher-level device description where the devices are referenced by their features, rather than by name. For example:

 {'vendor':'SAMSUNG', size:'256G', 'rotational':'no'}

The above example is from a proposed feature coming in ceph-ansible tracked by https://github.com/ceph/ceph-ansible/issues/1084 and this proposal is contingent on that feature. Assuming that feature merges, this proposal's implementation will result in updates to TripleO to support a syntax like the above in addition to documentation and CI updates to test the above.