MUC: Don't default component admins to being room owners
This change has various technical and social benefits. If ownership of a MUC
is really needed, it can be gained using the 'Set affiliation' ad-hoc command
or prosodyctl shell.
Example client incompatibility with the old behaviour:
- https://github.com/monal-im/Monal/issues/1085
-- 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