Move libvirt's qemu configuration dir to state fs

We need libvirt domain entries created by Nova in to persist across
image upgrades.  Otherwise, instances are effectively removed from the
hypervisor after a new image deploys with an empty libvirt config tree.
This registers /etc/libvirt/qemu as a stateful path and ensures persistent
domain configurations across upgrades.

Change-Id: I419bb25069314c7e639f980b5c236711b2d58edc
Closes-bug: #1336115
Merge "Move libvirt's qemu configuration dir to state fs"