Add possibility to specify multiple disks in 'virt' module
Add possibility to specify multiple disks in 'virt' module

Now disk profiles can contain multiple disks:

- backward compatible: if 'image' argument is set for virt.init()
  *and* 'image' attribute is missing for the first disk, then the
  first disk will use the 'image' from the method arguments

- multiple disks can be specified for a disk profile, see pillar
  example below

- if 'size' attribute set for qcow2-based image, then resulting
  image will be resized to the 'size' capacity (author: Ondrej Smola)

- empty disks allowed ('size' attribute is mandatory in this case)

Example disk profile 'three_disks':

virt:
  disk:
    three_disks:
      - system:
          size: 4096
          image: http://path/to/ubuntu.qcow2
      - repository_snapshot:
          size: 8192
          image: /var/lib/libvirt/images/snapshot.qcow2
      - cinder-volume:
          size: 16384

saltstack/salt,saltstack/salt,saltstack/salt,saltstack/salt,saltstack/salt