Backend Parent:

	- Spawned by frontend when it decides it needs a backend and a
		be parent is not running.

	- Signalled by frontend when another backend is needed.

	- Waits for backends to complete and removes their be record
		from the temp file.

	- If parent is lost (can't be signalled), then the group is
	 	invalidated

	- Is used to collect signal exit status for killed backends and provide
		the correct exit status for the frontend
