ceph-config: default devices and lvm_volumes when setting num_osds
ceph-config: default devices and lvm_volumes when setting num_osds

This avoids errors when the osd scenario choosen does not require
setting devices or lvm_volumes. The default values for these are not
set because they exist in the ceph-osd role, not ceph-defaults.

Signed-off-by: Andrew Schoen <1bb641dc23c3a93cce4eee683bcf4b2bea7903a3@redhat.com>

fgal/ceph-ansible,ceph/ceph-ansible,ceph/ceph-ansible,fgal/ceph-ansible