virt/propcan: Add a update method into PropCanBase class.

Signed-off-by: Dongsheng Yang <yangds.fnst@cn.fujitsu.com>
utils_test/libvirt: Add a function pci_label_from_address.

Signed-off-by: Dongsheng Yang <yangds.fnst@cn.fujitsu.com>
libvirt_xml/nodedev_xml: Add virt_functions in PCIXML class.

This patch add a support for virtual functions pci devices.

Signed-off-by: Dongsheng Yang <yangds.fnst@cn.fujitsu.com>
Merge pull request #1476 from yangdongsheng/pci_passthrough

libvirt_xml: Improvement for nodedev_xml.