mod_s2s_auth_dane: Fix traceback in DANE-TA check because unpack() moved It moved into the table package in Lua 5.2, error happens when compat is disabled or gone (ie 5.3+). This happened in DANE-TA, which is disabled by default.

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

``` sh
prosodyctl mod_listusers
```