iptables: Limit smokescreen port 4750, add camo port.

Limit incoming connections to port 4750 to only the smokescreen host,
and also allow access to the Camo server on that host, on port 9292.

puppet/zulip_ops/templates/iptables/rules.v4.erb

@@ -40,9 +40,14 @@
 -A INPUT -p tcp --dport https      -j ACCEPT
 -A INPUT -p tcp --dport postgresql -j ACCEPT
 
+<% if @fqdn.include? "smokescreen" -%>
 #                       Smokescreen proxy
 -A INPUT -p tcp --dport 4750       -j ACCEPT
 
+#                       Camo proxy
+-A INPUT -p tcp --dport 9292       -j ACCEPT
+<% end -%>
+
 #                       statsd
 -A INPUT -p udp --dport 8125       -j ACCEPT
 <% end -%>