libvirt.test: Add '--update-cpu' test for dumpxml

Signed-off-by: Li Yang <liyang.fnst@cn.fujitsu.com>
libvirt.test: Add 'security-info' test for virsh dumpxml

Signed-off-by: Li Yang <liyang.fnst@cn.fujitsu.com>
Merge pull request #112 from liyangfnst/dumpxml

libvirt.test: Add '--update-cpu' and '--security-info' test for dumpxml