utils_libvirtd: if libvirt is not availible in host, No error, but a warning.

Signed-off-by: yangdongsheng <yangds.fnst@cn.fujitsu.com>
Merge pull request #624 from yumingfei/aexpect_spawn

Aexpect spawn's definition
Merge pull request #622 from yangdongsheng/utils_libvirtd

utils_libvirtd: if libvirt is not availible in host, No raising Error, but logging.warning.
virttest.libvirt_xml: Add get_first_mac_by_name method for VMXML class.

Signed-off-by: Yu Mingfei <yumingfei@cn.fujitsu.com>
virttest.utils_libguestfs: Enhancements for module.

Signed-off-by: Yu Mingfei <yumingfei@cn.fujitsu.com>
libguestfs.tests: Add module for guestfishing operated disk.

Signed-off-by: Yu Mingfei <yumingfei@cn.fujitsu.com>