Update docker-py

From https://github.com/bfirsh/docker-py/commit/4bc5d27e51cc9afecfbc1d566b413f4d45203823
Brought branch up to date with latest master. Includes an updated docker client with container creation entrypoint support.
Updated recreate_containers to remove any entrypoint set for the intermediate container.
Updated test coverage to check if an container is recreated with an entrypoint it is handled correctly.