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This increases build time, and might hurt disk performance for kvm/qemu
a bit. So we disable it by default. But will be useful for docker images
etc.

This significantly reduces image size, and since we're not using the
images interactively does not sacrifice anything we care about.

Remove the ubuntu1804 image. Base only has basic tools, no build tools
or libraries. Install build deps in nopaxos, mtcp, and tas images.

Necessary for for building the tas image.

Just run different scripts inside. This avodis lots of duplication in
the jsons.