fix(storages): pool pages work while a volume is cloned, failed pools are undefined

- libvirt refuses to refresh a pool while a volume is cloned in it. The pool
  page, the volume list of the VM and create pages, upload planning and the
  API no longer fail on that refusal; they use the list libvirt has.
- A new pool that does not start (unreachable NFS server, a device LVM
  cannot use) is undefined again, so the name is free for another try.
- A pool reporting no size, such as an iSCSI pool without LUNs, shows its
  page instead of a division error.
- Each clone dialog shows its own format and metadata rows, so a format
  is never shown without Convert ticked and silently ignored.
- The new-volume size is labelled in GiB and is at least 1; an inactive
  pool shows no "None" volume count.

storages/forms.py

@@ -73,7 +73,7 @@ class CreateVolumeForm(forms.Form):
         required=True,
         choices=(("qcow2", "qcow2 (recommended)"), ("qcow", "qcow"), ("raw", "raw")),
     )
-    size = forms.IntegerField()
+    size = forms.IntegerField(label=_("Size (GiB)"), min_value=1)
     meta_prealloc = forms.BooleanField(required=False)
 
     def clean_name(self):