Bug 11499: UT: Make zebra_setup.pl correctly set indexing mode

Bug 11499: UT: Make zebra_setup.pl correctly set indexing mode

By adding the relevant environment variables to the script the generated
koha-conf.xml file for the unit tests is correct now.

Test plan:
- Verify that tests pass now:
  $ prove -v t/db_dependent/Search.t 2> /dev/null | grep 11499

Sponsored-by: Universidad Nacional de Cordoba
Signed-off-by: Galen Charlton <gmc@esilibrary.com>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Passes unit test, koha-qa.pl

Signed-off-by: Galen Charlton <gmc@esilibrary.com>
(cherry picked from commit 5666ed77a34d48aa10e1ad2b1f06d99c0553644f)
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>