[ticket/12873] Test the correct identifier in \phpbb\db\tools

https://tracker.phpbb.com/browse/PHPBB3-12873
https://tracker.phpbb.com/browse/PHPBB3-12770

PHPBB3-12770
PHPBB3-12873
It could be very very expensive on big boards... but it is very mattering if we have 2 different index names?