mod_s2s_keepalive: Fix identification of replies (error-replies included) Typo? This condition is supposed to filter out get and set (and anything else), not errors, which can still mean that there's connectivity, just no handling of XEP-0199.

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

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