deconz doesn't handle SIGTERM and terminates with code 143 (128 + 15
(SIGTERM) instead of 0. This results in systemd marking the service as
failed when a user stops it (with `systemctl stop deconz`). Fix it by
treating code 143 as success.
It should be curl -L (follow redirects), not curl -l (FTP directory
listing option). I know because it's my mistake.
Fixes: d4b989cafc ("nixos/deconz: delay signalling service readiness until it's actually up")
