Clean up our disk image and mountpoint

We create a disk image during setup, which now gets persisted in
/etc/fstab across boots. Clean that up when we're instructed to
do a clean operation.

Depends-On: https://review.opendev.org/#/c/743007/
Change-Id: I54a6b637266c2f182eeece8942156b07581a7f0b

devstack/lib/ceph

@@ -332,6 +332,9 @@ function cleanup_ceph_remote {
         sudo ceph -c ${CEPH_CONF_FILE} osd pool delete $NOVA_CEPH_POOL $NOVA_CEPH_POOL \
             --yes-i-really-really-mean-it > /dev/null 2>&1
     fi
+
+    # Clean up the disk image and mount that we created
+    destroy_disk ${CEPH_DISK_IMAGE} ${CEPH_DATA_DIR}
 }
 
 function cleanup_ceph_embedded {