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.

This reapplies a previously reverted fix, this time including the proper
element-deps.

Change-Id: I716b9e6f3c8d36c56749b7de0915e5a3d2eb1973
Closes-bug: #1336115
Merge "Move libvirt's qemu configuration dir to state fs"