replaced 'session' with 'origin' in push_disable session is not defined in this function, trying to access it leads to an error. The correct reference seems to be 'origin'. (This may have come about by copying from the similar code in process_stanza_queue.)

This module lets you block connections to any remote servers not on a
whitelist.

``` {.lua}
s2s_whitelist = {
    "example.org",
}
```