Add Virtuozzo Storage Volume Driver

Add Virtuozzo Storage Volume Driver

Add a volume driver which can use Virtuozzo Storage, which
has filesystem interface and so volume driver has a similar
workflow to NFS and SMBFS drivers.

At this point the driver contain minimal set of features. Because
I think some refactoring should be done in RemoteFS drivers before
further development. For example code, which deals with image formats
should go to the RemoteFS class. So I don't add qcow2 images support
in this patch.

Change-Id: If491c4220a77995d0c4247d152b49b0ff3fb0902
Partially-implements: blueprint virtuozzo-cloud-storage-support