[kolla-ansible] Nova + ceph cache mode

Hey Folks, Is it possible to use "cache=none" and "io=native" values with a kolla-ansible deployed cloud that uses a Ceph backend? Looks like that it's hard coded to use writeback for caching when the Nova backend is rbd. No globals.yaml overrides. https://github.com/openstack/kolla-ansible/blob/8d6b5de4c19681dd6cbec45d8031... Cheers Michael