filestore-to-bluestore: fix undefine osd_fsid_list

If the playbook is used on a host running bluestore OSDs then the
osd_fsid_list won't be filled because the bluestore OSDs are reported
with 'type: block' via ceph-volume lvm list command but we are looking
for 'type: data' (filestore).

TASK [zap ceph-volume prepared OSDs] *********
fatal: [xxxxx]: FAILED! =>
  msg: '''osd_fsid_list'' is undefined

Closes: https://bugzilla.redhat.com/show_bug.cgi?id=1729267

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

infrastructure-playbooks/filestore-to-bluestore.yml

@@ -207,6 +207,7 @@
                 CEPH_CONTAINER_IMAGE: "{{ ceph_docker_registry + '/' + ceph_docker_image + ':' + ceph_docker_image_tag if containerized_deployment else None }}"
                 CEPH_CONTAINER_BINARY: "{{ container_binary }}"
               loop: "{{ osd_fsid_list }}"
+              when: osd_fsid_list is defined
 
             - name: ensure all dm are closed
               command: dmsetup remove "{{ item['lv_path'] }}"