udp2log: rsync, add ferm service for rsyncd

As outlined in Change-Id: Ibf3af60a8932325f1 we need
to add ferm firewall holes for all TCP services on nodes
having udp2log, so that later we can add base::firewall
with the default DROP policy and then get rid of the entire
old iptables class.

This is adding one for rsync on 873. Using the source IP
addresses already used in $hosts_allow a few lines above.

Change-Id: I50c83e4256b7589ea45b35342b1c50fb5127d865
Merge "udp2log: rsync, add ferm service for rsyncd" into production