After some investigation, I found the problem: juju uses 'hostname -f' to find the hostname used for the 'public-address' field. That hostname is set by cloud-init which, in turn, fetches that from the metadata service.
After some investigation, I found the problem: juju uses 'hostname -f' to find the hostname used for the 'public-address' field. That hostname is set by cloud-init which, in turn, fetches that from the metadata service.