Closes#8158
This fixes the following errors when attempting to auto-complete with packer v.1.4.3:
(installed via Homebrew on macOS Mojave)
`invalid option definition: -except=[(foo,bar,baz) Validate all builds other than these].`
`invalid option definition: -only=[(foo,bar,baz) Validate only these builds].`
Removes the push command and the Atlas post-processor. Please see our
guide on building immutable infrastructure with Packer on CI/CD for
ideas on implementing these features yourself.
https://www.packer.io/guides/packer-on-cicd/