In 5532065d0690645f0a813fed6e68163b0f4774d4, acme was changed to be
RemainAfterExit=true, but `postRun` commands are implemented as
`ExecStopPost`. Systemd now considers the service to be still running
after simp_le is finished, so won't run these commands (e.g. to reload
certificates in a webserver). Change `postRun` to use `ExecStartPost` to
ensure the commands are run in a timely manner.