cloud_libvirt: experimental libvirt cloud provider.
cloud_libvirt: support for multiple nics on different symbolic networks.
cloud_libvirt: json profile for deploying to libvirt environment.

hosts to deploy to are selected according to their perceived load instead
of the previously used random selection.
cloud_libvirt: no_tty, no_verify and keyfile parameters.

If libvirt client version is lower than 0.9.4 start the deployment by
connecting to the hosts manually to accept host keys.
cloud_libvirt: attempt to remove "Storage volume not found" errors

* destroy domain before deleting disks
* ignore "Storage volume not found" when deleting disks
cloud_libvirt: use paramiko for ipv6/ipv4 tunneling.
cloud_libvirt: tuned ipv4 address retrieval logic and added more progress logging
cloud_libvirt: Delete snapshots before deleting VM.
cloud_libvirt: use SRV records to access host groups.

* handle DNS response truncation (retry with TCP)
* use SRV priority and weight to balance VMs
* delete all existing vms before cloning any new ones
cloud_libvirt: allow defining multiple disks, new and cloned.
cloud_libvirt: support for LVM (and other block dev based) storage provisioning.
cloud_libvirt: updates

* delete existing storage volume if overwrite flag is set
* fix block device usage in domain enumeration
cloud_libvirt: 120 second timeout for getting guest addresses.

* disconnect from libvirt hypervisors when done.
cloud_libvirt: set provider id correctly.
cloud_libvirt: use of other cloud providers possible without all libvirt deps

Missing libraries (libvirt, pydns) no longer prevents using other
cloud provider types.
cloud_libvirt: retry on DNS call timeouts
cloud_libvirt: workaround transient "connection reset by peer" errors
cloud_libvirt: allow cpu mode setting and default to 'host-model'.

host-model uses the best virtual cpu model qemu can emulate, presenting more
capabilities to the guests while still allowing migration between different
hardware platforms.
cloud_libvirt: do not try to resolve ipv6 addresses.
cloud_libvirt: don't delete existing vms when reinit=False.