[~] BO : Fix search conf indexation amount (PSCSX-758)

Fixes http://forge.prestashop.com/browse/PSCSX-758

The indexation values (amount / total) are wrong because the SQL query doesn't filter by product_shop "visibility" and "active" state (but the Search::indexation method does)
Merge pull request #1424 from axometeam/patch-25

[~] BO : Fix search conf indexation amount (PSCSX-758)