Comment 2 for bug 1683730

@jichenjic to delete a non-empty cell we need to delete its mapping to hosts/instance first. Which actually means that we need to remove hosts from cell. then only we can delete any cell.

One thing can be done here. We have a CLI to delete an empty cell - "nova-manage cell_v2 delete_cell --cell_uuid <cell_uuid>". we can append "-f" or "--force" to that existing command to first delete all the mappings and then removing cells.