This fixes an issue where it is not possible to customise the `host`
config option in the Nova Compute Ironic config file without breaking
detection of the service.
This is a backwards compatible fix, which allows a user to set the
`host` config option using Ansible host or group vars.
Other reasons for not using the default host setting of
`{{ ansible_hostname }}-ironic` are covered in [1].
[1] https://specs.openstack.org/openstack/nova-specs/specs/2024.1/approved/ironic-shards.html#migrate-from-peer-list-to-shard-key.
Closes-Bug: #2056571
Change-Id: I9b562f6a5722f21b7dbec2a4d53a46a57c829155
ac7c1e96e3
