Loop improvements

[randy-sab-roy]

📖 Description

This PR improves the run loop by checking for changes in the .env which allows us to change stuff on the fly.

• The .env is reloaded at the beginning of the loop
• Before starting the runner, the script will now validate that the image exist, and attempt to pull it if it doesn't.
• The script will check for a SCHEDULE_SHUTDOWN flag in the .env and will shutdown if it is set to true. This allows us to turn off the runner when it has completed its current job.
• SIGTERM events will now be intercepted by the script to allow the cleanup to work when it is running as a service

[remi]

👌