mod_restrict_xmpp: Treat archive query as a read despite using iq-set XEP-0313 uses iq-set to initiate a query, but unlike many other uses of iq-set, this does not mutate anything on the server, so it should not be treated as a write request.

This module adds a command to `prosodyctl` for listing users.

``` sh
prosodyctl mod_listusers
```