[fix] Use metadata to map instances to lease
The lease id recently disappeared from the availability zone info in servers. It broke the configure part of an appliance, as we were using this info to create an ansible inventory for the stack. Unfortunately, after an exchange with Chameleon staff, it became clear that this "feature" wasn't intended.
We now add metadata to our appliance template, allowing us to add the arbitrary info we need to the server info. This way we can filter as we want. This should make the script more future-proof.