Fix reset interwiki table between tests

Fix reset interwiki table between tests

This fixes the following SQL error, when the interwikilinks table was
marked as used:
Fatal error: Uncaught exception 'Wikimedia\Rdbms\DBQueryError' with message 'A database query error has occurred. Did you forget to run your application's database schema updater after upgrading?
Query: INSERT  INTO `unittest_interwiki` (1,2,3) VALUES ('Array','Array','Array')
Function: MediaWikiTestCase::resetDB

iterator_to_array on the result of the select of the interwiki table
returns an array with the first entry having the key 1. For
multi insert to work, the array must start on 0.
Change-Id: I3dc1be9e2f016709f451fe6e8d7cc60862c1ffea