Currently, `public_ips` will contain a single `None` element, if `primaryIpAddress` attribute is not available (same goes for private ips).

Can you please change it so the list will be empty if there are no IP addresses? So something like this:

```python
public_ips = []

if 'primaryIpAddress' in host
    public_ips.append(host['primaryIpAddress'])
```

Tests for this functionality would also be good.