Endpoint script doesn't handle SIGTERM properly

[ciera]

Our endpoint script doesn't handle SIGTERM properly. This means that when we run docker stop, we get a SIGTERM, disregard it, wait until the timeout, then receive the SIGKILL.

Workaround: we can run with docker stop -t 0, which will immediately SIGKILL. Fine for now since we don't have any cleanup, but we should probably do this correctly...

Lots of info about this:
The original discussion on github: moby/moby#3240
Docker and PID 1: http://blog.phusion.nl/2015/01/20/docker-and-the-pid-1-zombie-reaping-problem/
Exec v. shell form (we are using exec form): https://docs.docker.com/reference/builder/#entrypoint
Other projects that ran into this, and their solutions:
moby/moby#2436
https://gist.github.com/zba/27d9e54e7293c1bb2da4
http://veithen.github.io/2014/11/16/sigterm-propagation.html (<-----we may need this one)
moby/moby#3766

Most people seem to solve this problem by (1) using exec mode when starting their service (we already do that) and (2) if the entrypoint is a shell script, using exec when starting their service there. This however, will only work if you have a single service you are starting. We have several.

I suspect this means we need to actually trap the signal in our shell script.