ceph-volume: handle idempotency with batch and explicit scenarios

ceph-volume: handle idempotency with batch and explicit scenarios

If you used --wal-devices or --db-devices with batch and too
many devices are filtered out then a RuntimeError was raised.

However, if --report and --format=json is used then we
should return valid json indicating that no OSDS will be created
so that ceph-ansible and other systems can use that for idempotency checks.

Resolves: rhbz#1827349

Signed-off-by: Andrew Schoen <aschoen@redhat.com>