CloningVolumeSource doesn't set volume Capacity

[richt-volx]

I tried creating an image by cloning an existing volume (a qcow2 cloud-image I'd downloaded), but I wanted to resize it, so I added a capacity = element to the volume definition:

volume {
    name  = "my-new-root-volume"
    bus   = "virtio"
    pool  = "default"
    alias = "artifact"
    source {
      type   = "cloning"
      pool   = "default"
      volume = "noble-server-cloudimg-amd64.img"
    }
    capacity = "20G"
  }

This doesn't resize the volume, so the image ends up whatever the size of the source volume is.

This looks to be the same issue as #52 , I patched in a call to Driver.StorageVolResize, following the same pattern as the fix for that (6c1e562) and it now works for me.

Let me know if it would be helpful to open a PR with my fix.