simple_cell_setup should not exist with 1 when there is no compute hosts

[Jeffrey Zhang]

    When deploying ironic environment, even though nova-compute is running,
    but there will be no compute nodes until adding ironic nodes. And the
    user may not start nova-compute for some reason during fresh deployment.

    So stop return 1 when there is no compute hosts in simple_cell_setup.

[Jeffrey Zhang (jeffrey4l)]

This should be backported into ocata branch, imo.

[Sylvain Bauza (sylvain-bauza)]

We already discussed about that, and a change was also provided https://review.openstack.org/#/c/420079/ but if you see the status of that change, it was abandoned.

If you look at the reason why it was abandoned, it is because we made a consensus on leaving simple_cells_setup() as much simple and opiniated as possible and rather provide a step-by-step experience for operators deploying CellsV2 that you can see described in https://docs.openstack.org/developer/nova/cells.html#first-time-setup

[Jeffrey Zhang (jeffrey4l)]

But this will be failed when deploy nova+ironic only.

anyone considered this one?