When using non lvm scenarios (collocated or non-collocated) then the
disk_list variable isn't set because this is done during the ceph-osd
role (start_osds.yml) which isn't executed in the docker2podman
playbook.

Closes: https://bugzilla.redhat.com/show_bug.cgi?id=1862046



Signed-off-by: Dimitri Savineau <dsavinea@redhat.com>