vcpu properties gathered from query-hotpluggable cpus need to be passed
back to qemu. As qemu did not use the node-id property until now and
libvirt forgot to pass it back properly (it was parsed but not passed
around) we did not honor this.
This patch adds node-id to the structures where it was missing and
passes it around as necessary.
The test data was generated with a VM with following config:
<numa>
<cell id='0' cpus='0,2,4,6' memory='512000' unit='KiB'/>
<cell id='1' cpus='1,3,5,7' memory='512000' unit='KiB'/>
</numa>
Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1452053
