Eu examinei os documentos da libvirt e descobri o seguinte:
serial
If present, this specify serial number of virtual hard drive. For example, it may look like WD-WMAP9A966149.
Assim, o bloco XML que você tem acima se tornaria:
<disk type='file' device='disk'>
<driver name='qemu' type='raw'/>
<source file='/var/lib/libvirt/images/shared-01-02-00.img'/>
<target dev='sda' bus='scsi'/>
<address type='drive' controller='0' bus='0' unit='0'/>
<serial>some-arbitrary-serial</serial>
</disk>