Glance reported down

We're running openstack yoga and the openstack-exporter (latest/stable, rev 47) reports glance as down although it is healthy:
```
ubuntu@juju-30dcdf-5-lxd-11:~$ curl -s localhost:9180/metrics | grep glance
# HELP openstack_glance_up up
# TYPE openstack_glance_up gauge
openstack_glance_up 0
```
here are the associated logs:
```
Jun 23 13:04:47 juju-30dcdf-5-lxd-11 charmed-openstack-exporter.service[931849]: ts=2025-06-23T13:04:47.038Z caller=exporter.go:132 level=error err="Failed to collect metric for exporter" exporter=glance error="failed to collect metric: images, error: json: cannot unmarshal string into Go struct field .images.tmp.Properties of type map[string]interface {}"
Jun 23 13:04:46 juju-30dcdf-5-lxd-11 charmed-openstack-exporter.service[931849]: ts=2025-06-23T13:04:46.914Z caller=exporter.go:106 level=info msg="Collecting metrics for exporter" exporter=openstack_glance metrics=images
Jun 23 13:04:46 juju-30dcdf-5-lxd-11 charmed-openstack-exporter.service[931849]: ts=2025-06-23T13:04:46.914Z caller=exporter.go:132 level=error err="Failed to collect metric for exporter" exporter=glance error="failed to collect metric: image_bytes, error: json: cannot unmarshal string into Go struct field .images.tmp.Properties of type map[string]interface {}"
Jun 23 13:04:46 juju-30dcdf-5-lxd-11 charmed-openstack-exporter.service[931849]: ts=2025-06-23T13:04:46.790Z caller=exporter.go:106 level=info msg="Collecting metrics for exporter" exporter=openstack_glance metrics=image_bytes
Jun 23 13:04:46 juju-30dcdf-5-lxd-11 charmed-openstack-exporter.service[931849]: ts=2025-06-23T13:04:46.790Z caller=exporter.go:187 level=info msg="Adding metric to exporter" metric=image_created_at exporter=glance
Jun 23 13:04:46 juju-30dcdf-5-lxd-11 charmed-openstack-exporter.service[931849]: ts=2025-06-23T13:04:46.790Z caller=exporter.go:187 level=info msg="Adding metric to exporter" metric=image_bytes exporter=glance
Jun 23 13:04:46 juju-30dcdf-5-lxd-11 charmed-openstack-exporter.service[931849]: ts=2025-06-23T13:04:46.790Z caller=exporter.go:187 level=info msg="Adding metric to exporter" metric=images exporter=glance
```

I am aware that this has been [reported upstream](https://github.com/openstack-exporter/openstack-exporter/issues/400), however, we should track this here as well.