Dockerfile entrypoint breaks old docker run syntax

[danielhoherd]

This change of adding a Dockerfile entrypoint alters the functionality and breaks the previous docker run syntax.

$ docker images | grep -E 'TAG|yelp'
REPOSITORY                TAG                       IMAGE ID       CREATED        SIZE
yelp/docker-custodian     latest                    31133b4f742b   3 years ago    60.2MB
$ docker run --rm -ti --mount "type=bind,src=/var/run/docker.sock,dst=/var/run/docker.sock" yelp/docker-custodian dcgc --help
usage: dcgc [-h] [--max-container-age MAX_CONTAINER_AGE]
            [--max-image-age MAX_IMAGE_AGE] [--dangling-volumes] [--dry-run]
            [-t TIMEOUT] [--exclude-image EXCLUDE_IMAGE]
            [--exclude-image-file EXCLUDE_IMAGE_FILE]
            [--exclude-container-label EXCLUDE_CONTAINER_LABEL]

$ docker images | grep -E 'TAG|yelp'
REPOSITORY                       TAG            IMAGE ID       CREATED        SIZE
yelp/docker-custodian            latest         3ad4ce06f7cf   7 weeks ago    62.3MB
$ docker run --rm -ti --mount "type=bind,src=/var/run/docker.sock,dst=/var/run/docker.sock" yelp/docker-custodian dcgc
usage: dcgc [-h] [--max-container-age MAX_CONTAINER_AGE] [--max-image-age MAX_IMAGE_AGE] [--dangling-volumes] [--dry-run] [-t TIMEOUT] [--exclude-image EXCLUDE_IMAGE] [--exclude-image-file EXCLUDE_IMAGE_FILE]
            [--exclude-container-label EXCLUDE_CONTAINER_LABEL]
dcgc: error: unrecognized arguments: dcgc

It also appears that this behavior change was not mentioned in the changelog. Also the yelp/docker-custodian docker hub documentation still says to use the old syntax.