mod_storage_xmlarchive: Fix "user" iteration API Fixes use in prosody-migrator. Otherwise this particular API is not used much, or this would have been noticed before. Usually it is a different store like 'accounts' that is responsible for providing the authoritative list of users. Thanks Ge0rG for testing

This module lets you block connections to remote servers at the s2s
level.

``` {.lua}
modules_enabled = {
    -- other modules --
    "s2s_blacklist",

}
s2s_blacklist = {
    "proxy.eu.jabber.org",
}
```