rpearce/grichards: Whole bunch of fix up's.

  * Fix regex's for lv data for vg function
  * Rename GB function as it uses KB not bytes
  * Convert output from du to GB
  * Ensure output from du is apparent size (as we thin provision vms when using Image, see ->
      * http://serverfault.com/questions/428868/does-kvm-raw-images-support-preallocation