Update ubuntu images with ubuntu-minimal and apt-cache translations exclusion

So this update is actually two-fold.  It includes the same new "Translations" exclusions from the debian images (and the fix to keep us from growing 40MB on the first "apt-get update"), but it also includes ubuntu-minimal, since we're legally required to include that metapackage and its deps to call this image "ubuntu".  It moves our image size to be around 120-140 MB (from the sparse roughly 100 MB it is now), but that's a necessary evil since we'd like to have Ubuntu. :)