libvirt.test: Add some more case for ping commond of qga

1.Add halt status test
2.Add pm-suspend status test
3.Add guest cpu busy test

Signed-off-by: Li Yang <liyang.fnst@cn.fujitsu.com>
libvirt.test: Add fsfreeze command for qemu-agent-command test

Signed-off-by: Li Yang <liyang.fnst@cn.fujitsu.com>