xl: use libxl_domain_info to get the uuid in printf_info

xl: use libxl_domain_info to get the uuid in printf_info

If there is no UUID specified in the config file, we generate one during
the _parsing_ process. Since xl list -l parses the config file again,
the UUID will be generated again in this case and the reported
version does probably not match the used one.
Fix this by retrieving the UUID from dominfo (like xl list -v does).

Signed-off-by: Andre Przywara <andre.przywara@amd.com>
Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
committer: Stefano Stabellini <stefano.stabellini@eu.citrix.com>