Ceph 3 does not allow to create OpenStack Cinder volume: "Insufficient free space for volume creation. Total capacity is 0.00 on host" ; RHCS3 shows "usage: 0 kB used, 0 kB / 0 kB avail"

Issue

Unable to user Ceph 3 as a OpenStack Cinder back-end.

When creating a volume, it fails with error:

Failed to run task cinder.scheduler.flows.create_volume.ScheduleCreateVolumeTask;volume:create: No valid host was found. No weighed hosts available

The following WARNING messages are found in /var/log/cinder/scheduler.log:

2018-01-19 12:40:37.897 15853 WARNING cinder.scheduler.filters.capacity_filter [req-2ea2d9ff-ec9c-4ee5-a177-98af495cad4e 25d3de1c465b429999a08c58121f62ab ba132cb89ea6462691b923b292e42e5c - - -] Insufficient free space for volume creation. Total capacity is 0.00 on host cinder01.example.com@sas#sas.
2018-01-19 12:40:37.897 15853 INFO cinder.scheduler.base_filter [req-2ea2d9ff-ec9c-4ee5-a177-98af495cad4e 25d3de1c465b429999a08c58121f62ab ba132cb89ea6462691b923b292e42e5c - - -] Filter CapacityFilter returned 0 host(s)