virt-libvirt: Add virsh_define (and undefine) test

Thanks to Yu Mingfei <yumingfei@cn.fujitsu.com> for the original
virsh_rename_domain test which this is based upon. Exercises
virsh define and virsh_undefine plus auto-generated uuids.
Signed-off-by: NChris Evich <cevich@redhat.com>