Useless trap in the docker-entrypoint

[NicolasDorier]

Upon investigating a docker-compose down issue with clightning, I noticed that your trap. Does not work.

I am unsure about how to properly solve this issue. This would solve it, but sadly only available on v2 and not v3.

UPDATE: Init has been added back to v3.7. This would solve it, but I feel it is kind of a hack.

[NicolasDorier]

A solution is to use hypervisord to run the several processes or dumb-init.