libvirt: fully parse PCI addresses to integer data type

When parsing node device XML, the PCI addresses were left in their
string form, which is unhelpful for later code wishing to use their
raw values. Fully parse them to the integer form instead.

Blueprint: virt-driver-get-available-resources-object
Change-Id: I46b9c33e08122eb7c28601752ecfc652e09175c3
Merge "libvirt: fully parse PCI addresses to integer data type"