Horizon tries to create a volume even with a single node scenario

[Nobuto Murata]

When we follow the single node tutorial(s):
https://microstack.run/docs/single-node

OpenStack dashboard (Horizon) has persistent volume creation enabled by default in a VM launching dialogue. However, Cinder is not properly set up with a redundant storage yet in the single node scenario so the VM launch doesn't succeed unless the volume creation is explicitly disabled by the user whenever creating a new instance.

I think the following option could be set to False until Cinder (and Ceph) is properly configured with multiple nodes.

https://docs.openstack.org/horizon/latest/configuration/settings.html#create-volume
https://charmhub.io/horizon-k8s/configuration#default-create-volume