main/mqtt-exec: fix init.d script
2b9f3eec (main/mqtt-exec: fix init script, don't force supervise-daemon, 2023-12-06) broke the init.d script by removing the supervisor setting while not making sure that the process was run in the background.
This results in mqtt-exec running in the foreground when starting the service.
Fix this by providing command_background=true
, since mqtt-exec itself
has no options to background itself.
Fixes #15663 (closed)