Don't stop processes with "sigkill"

If we stop let's say php *daemons* with the init-script generated by this tool it can happen that we send a `SIGKILL` which can result in php zombies.
We should try to avoid that (see also https://github.com/cargomedia/puppet-cargomedia/issues/585), so I'd suggest to *not* sigkill, but rather time out and let the init-script fail.

@tomaszdurka fyi

Manpage of `start-stop-daemon`:
```
       -R, --retry timeout|schedule
              With  --stop,  specifies that start-stop-daemon is to check whether the process(es) do finish. It will check repeatedly whether any matching pro-
              cesses are running, until none are. If the processes do not exit it will then take further action as determined by the schedule.

              If timeout is specified instead of schedule, then the schedule signal/timeout/KILL/timeout is used, where signal is  the  signal  specified  with
              --signal.

              schedule  is  a  list of at least two items separated by slashes (/); each item may be -signal-number or [-]signal-name, which means to send that
              signal, or timeout, which means to wait that many seconds for processes to exit, or forever, which means to repeat the rest of the schedule  for-
              ever if necessary.

              If  the  end  of the schedule is reached and forever is not specified, then start-stop-daemon exits with error status 2.  If a schedule is speci-
              fied, then any signal specified with --signal is ignored.
```