retrieve public ip_address correctly

Hi, All:
  I found a bug happened when I specify to enable private network feature, The API provided by DO 
``` API
/v2/droplets/$DROPLET_ID.
```
will return 
```
{ "droplet" => {
     "networks": {
      "v4": [
        { 
           "ip_address": PRIVATE_ADDRESS,
          "netmask": "255.255.255.0",
          "gateway": "127.0.0.21",
          "type": "private"       
        },
        {
          "ip_address": "127.0.0.20",
          "netmask": "255.255.255.0",
          "gateway": "127.0.0.21",
          "type": "public"
        }
      ],
  }
}
```

Current ssh_info can not get the correct host information correctly.