Fix to support setting root disk size to minimum size required by image,
or 10gb if not avaiable.  better fix in develop for core/gce changes.
but for now this solves it without api changes.
FB 5765 Product size is not displayed under product dropdown list during
server launch
Merge pull request #225 from unwin/2014.11

FB 5765 Product size is not displayed under product dropdown list during