Bug 24993: Make sure SIP server is stopped before restarting it

Bug 24993: Make sure SIP server is stopped before restarting it

Sometimes doing koha-sip --restart instance happens too fast and
the SIP server is not started.

To test:
- have SIP enabled and running for your instance
- issue a restart, make sure it restarts
  sudo koha-sip --restart inst

Signed-off-by: Liz Rea <wizzyrea@gmail.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>