libvirt: Add numa tuning tests

    1) Positive testing
       1.1) get the current numa parameters for a running/shutoff guest
       1.2) set the current numa parameters for a running/shutoff guest
           1.2.1) set valid 'mode' parameters
           1.2.2) set valid 'nodeset' parameters
    2) Negative testing
       2.1) get numa parameters
           2.1.1) invalid options
           2.1.2) stop cgroup service
       2.2) set numa parameters
           2.2.1) invalid 'mode' parameters
           2.2.2) invalid 'nodeset' parameters
           2.2.3) change 'mode' for a running guest and 'mode' is not strict'
           2.2.4) change 'nodeset' for running guest with mode of interleave'
                  'interleave' or 'preferred' numa mode
           2.2.5) stop cgroup service

Signed-off-by: Alex Jia <ajia@redhat.com>