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
Welcome hackers!
This project accepts and *encourages* contributions. If you would like to get
involved you can join us on our mailing list and discussion rooms. More
information on these at https://prosody.im/discuss
Patches are welcome, though before sending we would appreciate if you read
docs/coding_style.md for guidelines on how to format your code, and other tips.
Documentation for developers can be found at https://prosody.im/doc/developers
Have fun :)