For the s390x architecture the sysfs core_id alone is not unique. As a
result it can happen that libvirt thinks there are less host CPUs available
than really present.
Currently, a logical CPU is equivalent to a core for s390x. We therefore
produce a fake core id from the CPU number.
Signed-off-by: NViktor Mihajlovski <mihajlov@linux.vnet.ibm.com>