Do not pluralize twice.

Even though it doesn't seem to fix the inflection bug of https://github.com/cakephp/cakephp/issues/4685 there is no need to pluralize twice - as tableize() already does that internally:

    $result = static::pluralize(static::underscore($className));

PS: I checked, and this is not an issue in 2.x - seems to be introduced in 3.0 only.