20.11.7

feat: add support for Slurm 20.11.7-1 (#29)

* feat: add support for Slurm 20.11.7-1

* chore: extend timeout

* style: run black formatter

* refactor: build docker image before install

* refactor: start services sequentially to avoid race conditions

* test: add checks for listening ports

fix: manually chmod slurmdbd.conf