scratchpad vdsm hook
====================
Hook creates a disk for a VM onetime usage,
the disk will be erased when the VM destroyed.
VM cannot be migrated when using scratchpad hook

Hook explicitly adds scratch disk as virtio 
device and thus will not work on systems without
virtio support.

syntax:
    scratchpad=size,path
    ie:
    scratchpad=20G,/tmp/myimg

    size: Optional suffixes "k" or "K" (kilobyte, 1024) "M" (megabyte, 1024k) and
          "G" (gigabyte, 1024M) and T (terabyte, 1024G) are supported.  "b" is ignored (default)

    note: more then one disk can be added:
    scratchpad=20G,/tmp/disk1,1T,/tmp/disk2
