Fixed graceful shutdown countdown for servers running in Docker

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• Migrations have been added if applicable
• Significant changes of this merge request have been added to the changelog.

• Changed server-cli/Dockerfile to use ENTRYPOINT to allow the veloren-server-cli process to receive signals sent by Watchtower. Previously our usage of CMD was resulting in the sh process being PID 1 rather than veloren-server-cli which meant the SIGUSR1 signal sent by Watchtower did not correctly initialise a 2 minute shutdown countdown .

From https://docs.docker.com/engine/reference/builder/#entrypoint The shell form prevents any CMD or run command line arguments from being used, but has the disadvantage that your ENTRYPOINT will be started as a subcommand of /bin/sh -c, which does not pass signals. This means that the executable will not be the container’s PID 1 - and will not receive Unix signals - so your executable will not receive a SIGTERM from docker stop .