mod_s2s_keepalive: Don't send whitespace keepalives before s2sin stream is open Could possibly result in whitespace before the XML and stream header, which isn't allowed by the parser. Don't think s2sout is affected, as the stream is opened early and doesn't have to wait for the other end. Thanks Ge0rG

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

``` sh
prosodyctl mod_listusers
```