fix(controller): restart celery or gunicorn in reload script

Previously the /app/bin/reload script invoked by confd assumed that pidfiles for celery and gunicorn always exist, which is not true in some failure cases. This only sends them a SIGHUP if they are running, and restarts them otherwise.

Fixes #1100.
You should re-copy this line from /bin/boot - we use an environment variable to toggle loglevel.