Fix: JcloudsLocation iptables disabling

- Allow it to be enabled via config OPEN_IPTABLES, but by default it's disabled.
- It was breaking things (due to `sudo -n` on centos, which needs fixed separately), when using jclouds to ssh to machine as part of creating the VM.
- Note the openIptables stuff is needed for (some) RHEL VMs, as by default the ports (other than 22) are locked down.