tests: Add nodeinfo test for non-present CPUs

tests: Add nodeinfo test for non-present CPUs

Some of the possible CPUs in a system might not be present, eg. they
might be defective or might have been deconfigured from the ASM console
in a Power system. Due to this fact, Linux keeps track of what CPUs are
possible and what are present separately.

This test uses the data from a system where not all the possible CPUs
are present to make sure libvirt handles this situation correctly.