authd child processes are only told about configured DNSBLs when the
configuration is being parsed.
This is bad, because when authd crashes or is killed, IRCd will restart
it, but will not tell it about any configured DNSBLs until IRCd is next
rehashed.
We already have a dictionary that stores configured DNSBLs (for hit
statistics for `STATS n'), so store the additional needed fields in
that structure, and loop over that dictionary's entries when authd is
restarted, sending the fields just as if the configuration were being
reloaded.