Previous code was confusing and brittle. For example, the full import
"source ./ci/test/00_setup_env.sh" and $PATH overwrite was not needed.
Fix it by simply copying the exe to /ci_retry and use that in
$CI_RETRY_EXE.
This is also a fix, because previously ci/lint_imagefile did use an
empty $CI_RETRY_EXE.
(Similar to the doc comment in ci/lint_imagefile)
Also, rename docker-entrypoint.sh to container-entrypoint.sh
Also, add copyright header to touched files.
