cpu_conf: Allow specification of 'units' for @memory on numa nodes.

cpu_conf: Allow specification of 'units' for @memory on numa nodes.

CPU numa topology implicitly allows memory specification in 'KiB'.

Enabling this to accept the 'unit' in which memory needs to be specified.
This now allows users to specify memory in units of choice, and
lists the same in 'KiB' -- just like other 'memory' elements in XML.

    <numa>
      <cell cpus='0-3' memory='1024' unit='MiB' />
      <cell cpus='4-7' memory='1024' unit='MiB' />
    </numa>

Also augment test cases to correctly model NUMA memory specification.
This adds the tag 'unit="KiB"' for memory attribute in NUMA cells.

Signed-off-by: Prerna Saxena <prerna@linux.vnet.ibm.com>
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>