Add an option to use host CM_REPO as docker_cm_repo

[arjunsuresh]

Currently in cm docker script the cm_mlops repo is always cloned from github. It'll be good to have an option to instead copy the specified cm_repo from the host machine.

[Oseltamivir]

Should we do this using an env var, CM_REPO_PATH, and checking if it is a dir with os.path.isdir() in script/build-dockerfile/customize.py?

[arjunsuresh]

Yes. That's correct. CM_REPO_PATH must also have _cmr.yml file in its root. The instead of doing cm pull repo we can use COPY command in dockerfile.