It is expected to be killed by a signal. Exit with returncode 0 anyway.
While at it, adjust it for current service format (executable, with
proper shebang).
To get endless sleep, `sleep inf` (or `sleep infinity`) can be used
instead of `sleep 365d`. Coreutils' sleep accepts any floating-point
number as an argument, which may be 'infinity', according to
`man strtod`.
