This is a rebase+resend of a patch from a few days ago[1]. Before importing an image, we
go out to Deltacloud to verify that the image actually exists on the provider.
As an added bonus, we get the image name from the cloud provider if it's present.
[1]
http://lists.fedorahosted.org/pipermail/aeolus-devel/2011-December/007556...