bfa054707b
firecracker/launch.py reimplemented docker build/image-exists/rm/exec/cp as private functions instead of the shared docker_mod used by the docker and macos-container backends. Switching to docker_mod dedupes the logic and gets --no-cache support for free (docker_mod.build_image already reads BOT_BOTTLE_NO_CACHE); docker_mod gains docker_exec/ docker_cp general-purpose helpers to cover what the private versions did.