add openstack

Guys, we need openstack iaas driver. 
Hi @sstrato, I'm testing the PR but I'm getting an error in this line.
I see the json is not returning info about AZ, but the machine is up and running with all correct metadata.

The return is that:
```
map[string]interface {}{
    "private":[]interface {}{
         map[string]interface {}{
             "OS-EXT-IPS-MAC:mac_addr":"fa:16:3e:53:14:0b", 
             "OS-EXT-IPS:type":"fixed", 
             "addr":"10.0.0.4",
             "version":4
          }
      }
}
```

I'm using the latest devstack with basic conf. 
I don't know if the code has a bug or I'm running the wrong version of OpenStack.