Compatibility with older version of virt-install

[anesheret]

* Ubuntu 20.04.6 LTS - compatibility
* Using `cloud-localds` - as described in cloud-init documentation
* `virsh` - auto remove all associated storage volumes

[holmanb]

• Using cloud-localds - as described in cloud-init documentation

But why?

cloud-localds is a wrapper around genisoimage, and cloud-utils isn't shipped to as many distros as genisoimage. The only benefit to cloud-localds, as I see it, is that it has a simpler command line invocation, but for a script like this that benefit is lost.

Also, information in the commit message about how virt-install fails and which version the change was made in would be valuable for reviewers and future users of this script.