libvirt: Add test module for virsh cpu-baseline

Signed-off-by: Li Yang <liyang.fnst@cn.fujitsu.com>
virt: Add virsh function for virsh cpu-baseline

Signed-off-by: Li Yang <liyang.fnst@cn.fujitsu.com>
Merge pull request #363 from liyangfnst/cpu_baseline

Add test for virsh cpu-baseline