Instance state has moved from field $5 to field $6

```ec2-describe-instances``` has changed its instance state output from field 5 to field 6, thus NAT_STATE needs to be updated.

```bash
$ ec2-describe-instances | grep INST | awk '{print $5}'
domU-12-31-39-07-D0-C6.compute-1.internal
domU-12-31-39-0E-E0-72.compute-1.internal
ip-10-12-85-167.ec2.internal
ip-10-62-75-27.ec2.internal
ip-10-80-150-207.ec2.internal
ip-10-60-10-141.ec2.internal
ip-10-238-226-152.ec2.internal

$ ec2-describe-instances | grep INST | awk '{print $6}'
running
running
running
running
running
running
running
```