lorawan-server doesn't properly shutdown in docker container

[lcse66]

Hi everyone.

The server running in the docker environment does not respond correctly to the shutdown request, but it is killed at the end of the timeout. A longer timeout produces no advantages. This behavior also causes side problems, including permanent errors in connectors when the connected service (e.g. mqtt broker) is running on the same server, and the server is being stopped. See also #771 #772. The issue can be verified by stopping the Lorawan container and measuring the shutdown time, which will be approximately 10 seconds (corresponding to the timeout for stopping the containers).

I know that this project is no longer being maintained for now, and I hope that it will be maintained again in the future. Best regards to @gotthardp for the excellent project.