virt-libvirt: Fix typo in virsh schedinfo(qemu) test

os.path.join("/cgroup/cpu", "/libvirt/qemu", "vm1") will
return "/libvirt/qemu/vm1", not "/cgroup/cpu/libvirt/qemu/vm1",
so I modify 'libvirt_cgroup_path' default value from
"/libvirt/qemu" to "libvirt/qemu"

Signed-off-by: Li Yang <liyang.fnst@cn.fujitsu.com>