mod_smacks: Ignore user when writing or reading session_cache on prosody 0.9 At least under some circumstances it seems that session.username is nil when a user tries to resume his session in prosody 0.9. The username is not relevant when no limiting is done (limiting the number of entries in the session cache is only possible in prosody 0.10), so this commit removes the usage of the username when accessing the prosody 0.9 session cache.

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

``` sh
prosodyctl mod_listusers
```