Avoid starting new jobs when TERM signal has been received.
Check refresh trigger in crunch-job instead of crunch-dispatch.

Crunch-job now checks the timestamp on the trigger file, rather than
waiting for crunch-dispatch notice that the trigger file appeared and
send HUP to its child processes. This way we don't depend on srun
doing what we want with signals.

See f99ffd6844ae9b88cfd17c8fe6e9fcc85a55d79c
Update comments in config/environment/ files.