virt-libvirt: fix bug in libvirt_xml

Signed-off-by: yangdongsheng <yangds.fnst@fujitsu.cn>
virt-libvirt: add configuration for virsh start

Signed-off-by: yangdongsheng <yangds.fnst@fujitsu.cn>
virt-libvirt: add test for virsh start

Signed-off-by: yangdongsheng <yangds.fnst@fujitsu.cn>