docker/docker_entrypoint.sh: Change from single quotes when looking for `$HOSTNAME` to double quotes.
docker/docker_entrypoint.sh: Change from single quotes when looking for `$HOSTNAME` to double quotes.

jakirkham/docker_basic,jakirkham/docker_ubuntu_drmaa_conda,jakirkham/docker_centos_drmaa_conda,nanshe-org/docker_centos_drmaa_conda,DudLab/docker_centos_drmaa_conda