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 remote servers at the s2s
level.

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