22317: Remove compute node image build.sh

22317: Remove compute node image build.sh

It is replaced by a process where the user edits Ansible and Packer
configuration files in place, then runs the appropriate tool directly.

While it was nice that build.sh saved you from knowing the details of
how tools were configured, it was becoming more difficult to maintain as
we grew more options. It also requires the user to remember the full
build.sh command they used if they want to build a new version for a new
base AMI, new Arvados release, etc. This improves that situation by
letting the user keep configuration files they can keep and update as
needed.

Arvados-DCO-1.1-Signed-off-by: Brett Smith <brett.smith@curii.com>