Bug 35954: Add --status to koha-plack

Bug 35954: Add --status to koha-plack

This adds a --status switch to the koha-plack command.

To test on ktd:
- Copy the script to /usr/sbin, so you run the modified script,
  and not the one installed by Koha:
  $ sudo cp debian/scripts/koha-plack /usr/sbin/
- Stop and start Plack for kohadev like so:
  $ sudo koha-plack --stop kohadev
  $ sudo koha-plack --start kohadev
  And make sure this reports the correct status, both when Plack
  is running and when it is not running:
  $ sudo koha-plack --status kohadev
- Make sure --status is mentioned here:
  $ sudo koha-plack --help
- See https://wiki.koha-community.org/wiki/Testing_man_pages for
  details on how to check the manual page for the command

Signed-off-by: Tadeusz Sośnierz <tadeusz@sosnierz.com>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>