qemu_driver: hook up query-cpu-model-comparison

qemu_driver: hook up query-cpu-model-comparison

This command is hooked into the virsh hypervisor-cpu-compare command.
As such, the CPU model XML provided to the command will be compared
to the hypervisor CPU contained in the QEMU capabilities file for the
appropriate QEMU binary (for s390x, this CPU definition can be observed
via virsh domcapabilities).

QMP will report that the XML CPU is either identical to, a subset of,
or incompatible with the hypervisor CPU. s390 can also report that
the XML CPU is a "superset" of the hypervisor CPU. This response is
presented as incompatible, as this CPU model would not be able to run
on the hypervisor.

Signed-off-by: Collin Walling <walling@linux.ibm.com>
Reviewed-by: Daniel Henrique Barboza <danielh413@gmail.com>
Reviewed-by: Boris Fiuczynski <fiuczy@linux.ibm.com>
Message-Id: <1568924706-2311-15-git-send-email-walling@linux.ibm.com>
Reviewed-by: Jiri Denemark <jdenemar@redhat.com>