when creating a new ovirt host, we should check that the necessary values were added before submitting the form
Otherwise we would fail:
Failed to create a compute v4 (oVirt) instance levi-voisard.tlv.redhat.com: Fault reason is "Invalid value". Fault detail is "The string '' isn't a valid value for the 'DiskInterface' enumerated type. Valid values are: 'ide', 'virtio_scsi', 'virtio', 'spapr_vscsi'.". HTTP response code is 400.