The /etc/init.d/iptables-persistent initfile changed to expect there to be two
files in /etc/iptables (rules.v4 and rules.v6) instead of a single rules file.
Several of our machines are currently running without iptables rules as a
result.
(imported from commit 266c2ff26b77f7c9ae793690b0d544ee4cfa5020)