fix properties' missing underline for VirtCPUTopology
fix properties' missing underline for VirtCPUTopology

According to the docs:
https://opendev.org/openstack/nova-specs/src/branch/master/specs/juno/implemented/virt-driver-vcpu-topology.rst,
cpu_maxsockets, cpu_maxcores, cpu_maxthreads should be cpu_max_sockets, cpu_max_cores, cpu_max_threads.

Change-Id: Ieecfb11928f74a504b35172a2c96d3a8cba057c0
Signed-off-by: Ning Yao <dd70006fc7bb50202c00379a3ab1a4f3073de3a7@unitedstack.com>

openstack/glance,openstack/glance,openstack/glance