Bug 17467: (follow-up) Make koha-zebra handle legacy script names

Bug 17467: (follow-up) Make koha-zebra handle legacy script names

This patch adds the new koha-zebra script the ability to handle being
called by other script names, for backwards compatibility with the legacy
koha-*-zebra scripts.

It is intended to be used in conjunction with a patch that replaces the old
koha-*-zebra scripts for symbolic links, pointing to the new koha-zebra script.

To test:
- Apply this patch
- Create symbolic links to the new script:
  vagrant@kohadevbox:~$ ln -s kohaclone/debian/scripts/koha-zebra koha-start-zebra
  vagrant@kohadevbox:~$ ln -s kohaclone/debian/scripts/koha-zebra koha-stop-zebra
  vagrant@kohadevbox:~$ ln -s kohaclone/debian/scripts/koha-zebra koha-restart-zebra
- Run:
  $ sudo ./koha-start-zebra kohadev
=> SUCCESS: Same behaviour than the koha-start-zebra script
- Run:
  sudo ./koha-stop-zebra kohadev
=> SUCCESS: Same behaviour than the koha-stop-zebra script
- Run:
  sudo ./koha-restart-zebra kohadev
=> SUCCESS: Same behaviour than the koha-restart-zebra script

Signed-off-by: Josef Moravec <josef.moravec@gmail.com>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>