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

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
