cputest: Switch host CPU data scripts to model expansion

cputest: Switch host CPU data scripts to model expansion

Instantiating "host" CPU and querying it using qom-get has been the only
way of probing host CPU via QEMU until 2.9.0 implemented
query-cpu-model-expansion for x86_64. Even though libvirt never really
used the old way its result can be easily converted into the one
produced by query-cpu-model-expansion. Thus we can reuse the original
test data and possible get new data from hosts where QEMU does not
support the new QMP command.

Signed-off-by: Jiri Denemark <jdenemar@redhat.com>