Bug 10712: Save missing config variables to install log

Bug 10712: Save missing config variables to install log

The variables for AUTH_INDEX_MODE and ZEBRA_TOKENIZER were not
being saved to the koha_install_log file.  As a result when using the
--prev-install-log option in Makefile.PL the user was still prompted
to select them.

This patch adds the appropriate variables to the list saved in
the install log.

To test:

On a (non-package) system installed/upgraded without the patch running
'perl Makefile.PL --prev-install-log /path/to/koha-install-log' will
still prompt you to choose authorities indexing mode and select
between chr and icu, after upgrading with this patch applied the same
command should get the responses from the install log and not require
user intervention.

The values can be seen written into misc/koha-install-log

Signed-off-by: Galen Charlton <gmc@esilibrary.com>
Signed-off-by: Chris Cormack <chris@bigballofwax.co.nz>
Signed-off-by: Galen Charlton <gmc@esilibrary.com>