mod_admin_blocklist: Add config option for which role(s) to consider (0.12+) Fixes that in trunk, a "prosody:operator" (formerly a global admin) is not considered a "prosody:admin", so those were not included in the set.

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

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