Bug 15188 - Fixes remove_unused_authorities.pl will delete all authorities if zebra...

Bug 15188 - Fixes remove_unused_authorities.pl will delete all authorities if zebra is not running

Test plan:

1) Shut down zebra: koha-zebra-ctl.sh stop
2) Execute the script: remove_unused_authorities.pl (with -t if you don't want to really delete from your database).
3) Check that the script would have deleted all the authorities (eg: 31449 authorities parsed, 31449 deleted and 0 unchanged because used).
4) Apply patch
5) Run, notice that the script dies because zebra is unavailable

Signed-off-by: Chris Cormack <chrisc@catalyst.net.nz>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Brendan A Gallagher <brendan@bywatersolutions.com>
(cherry picked from commit 128e7f54b17501ee43614aa8f8c50c3789921f08)
Signed-off-by: Julian Maurice <julian.maurice@biblibre.com>