small change, if len(words) > 1

I think we can do without this fact if we don't have words[1]?

```
fatal: [127.0.0.1] => failed to parse: Traceback (most recent call last):
  File "/Users/r498036/.ansible/tmp/ansible-1380830220.62-236999828409412/setup", line 3080, in <module>
    main()
  File "/Users/r498036/.ansible/tmp/ansible-1380830220.62-236999828409412/setup", line 2146, in main
    data = run_setup(module)
  File "/Users/r498036/.ansible/tmp/ansible-1380830220.62-236999828409412/setup", line 2084, in run_setup
    facts = ansible_facts()
  File "/Users/r498036/.ansible/tmp/ansible-1380830220.62-236999828409412/setup", line 2075, in ansible_facts
    facts.update(Network().populate())
  File "/Users/r498036/.ansible/tmp/ansible-1380830220.62-236999828409412/setup", line 1520, in populate
    default_ipv4, default_ipv6 = self.get_default_interfaces(route_path)
  File "/Users/r498036/.ansible/tmp/ansible-1380830220.62-236999828409412/setup", line 1567, in get_default_interfaces
    interface[v]['gateway'] = words[1]
IndexError: list index out of range
```