Remove our two borg hosts from the inventory

These are managed services and Ansible doesn't run on them. It got boring writing 'all,!rsync_net,!hetzner_storageboxes' in playbooks and ad-hoc commands, so remove these borg hosts from our inventory.

In the process to accomplish the above, I refactored the roles that set up our borg hosts to run on localhost; seems to work well and should prove more flexible if we were to get another storage box.

playbooks/hetzner_storagebox.yml

@@ -7,8 +7,8 @@
     - role: hetzner_storagebox
       backup_clients: "{{ groups['borg_clients'] }}"
       backup_dir: backup
-      backup_hostname: "{{ hetzner_storagebox_username }}.your-storagebox.de"
-      backup_username: "{{ hetzner_storagebox_username }}"
-      backup_password: "{{ hetzner_storagebox_password }}"
       storagebox_id: "{{ hetzner_storagebox_id }}"
+      storagebox_hostname: "{{ hetzner_storagebox_username }}.your-storagebox.de"
+      storagebox_username: "{{ hetzner_storagebox_username }}"
+      storagebox_password: "{{ hetzner_storagebox_password }}"
       tags: ["borg"]