ahbl is no longer being maintained and has been configured to return a
positive value for every host.  This means I get a cron warning every
day reporting that my mailserver is in ircbl.ahbl.org and
dnsbl.ahbl.org.

lukecyca/check-rbl#1 has removed ahbl from the blacklists that it
checks.  This just pulls in that change.

Unfortunately, ansible's get_url won't update files which have been
downloaded already unless you set force=yes, which will cause ansible to
pull down the file from github on every single run, which isn't really
acceptable.  I have filed ansible/ansible-modules-core#625 to ask that
get_url redownload if and only if the sha256sum differs.  In the
meantime, you have to manually delete /opt/check-rbl.pl before rerunning
ansible to pull in the update.  However, at least this will work fine
for new installs.

Related to #338 (though I don't know if it truly fixes it).