Open port 3306 on logstash.o.o

When mysql-proxy was being used we had to open port 4040 to allow
connections to the proxy. However, since that approach was abandoned
and simpleproxy is being used instead, it's just forwarding port 3306.
This commit fixes it by switch 4040 to 3306 in the firewall rules.

Change-Id: Ie6d04e20996ba4c7f567526a2428ce5015b8b135