util.jsonschema: Fix handling of `false` as schema Schemas can be either a boolean or a table (object) but since it only checked for truthiness, the case of `false` would be handled incorrectly. There seems to be no tests that cover `then` and `else` being `false`, only a couple that check the `if` keyword.

-- Prosody IM
-- Copyright (C) 2008-2010 Matthew Wild
-- Copyright (C) 2008-2010 Waqas Hussain
--
-- This project is MIT/X11 licensed. Please see the
-- COPYING file in the source package for more information.
--

module:set_global(); -- we're a global module

-- TODO delete this whole concept