Misc important fixes from BZ
- Fix crash when attaching/detaching non-existant PCI device (rhbz #510907)
- Fix QEMU guest name/uuid uniqueness checks (rhbz #507405)
- Fix to use correct pci_add/del syntax for QEMU (rhbz #499669)
- Relabel disks before hotplugging them to guest (rhbz #496442)
- Correctly handle 8-bit high bytes when escaping XML (rhbz #479517)