[ticket/12426] removing some complex logic

Removing some complex logic in memberlist.php
that was unneeded and renaming some vars

PHPBB3-12426
[ticket/12426] Removing unneded function and sql cache time

Removing unneded function
Removing SQL cache time

PHPBB3-12426
[ticket/12426] Variables rename

Changing function paramenters name
Changeing variable names

PHPBB3-12426