Bug 16084: [QA Follow-up] Correct three occurrences of __KOHA_CONF_DIR__

Bug 16084: [QA Follow-up] Correct three occurrences of __KOHA_CONF_DIR__

This bug correctly inserts substitutions for this variable.
Four occurrences will now be changed. The line for log4perl.conf is now
correct, but the three other changes point to a location that does not
exist: /etc/koha/sites/$instance/zebradb.
That should just be: /etc/koha/zebradb.
All three cases concern the explain files.

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Brendan Gallagher brendan@bywatersolutions.com