Fix Feature thePriceIs and fix Behat tests

If $data['price'] equal to 30 you throw the Exception because is not same cast of (float) $price.

You can add parameters of Scenario "Check the update quantity AJAX call" in features/frontend/shop/product.feature line 26 by identifier => 1017; quantity => 1; price => 1980; stock => 40 for throw exception without my correction