Function reapply 

pub fn reapply(unit: &UnitId, wait: Duration) -> Outcome

Rebuild the hold’s table in place (ExecReload runs the script’s reapply). A reload never lifts the hold, where a restart would run ExecStop (lift) first and let traffic through for a moment.

systemctl reload fails on an inactive unit, so one not active (the hold was stopped, or never started on this boot) is started instead.