Fix traceback when openstack do not have OS-EXT-IPS:type attached to add...

...ress

failed: [127.0.0.1] => {"failed": true, "parsed": false}
    invalid output was: Traceback (most recent call last):
      File "/tmp/ansible-1376083321.99-111209413777779/nova_compute", line 1176, in <module>
        main()
      File "/tmp/ansible-1376083321.99-111209413777779/nova_compute", line 239, in main
        _get_server_state(module, nova)
      File "/tmp/ansible-1376083321.99-111209413777779/nova_compute", line 198, in _get_server_state
        private = [ x['addr'] for x in getattr(server, 'addresses').itervalues().next() if x['OS-EXT-IPS:type'] == 'fixed']
    KeyError: 'OS-EXT-IPS:type'

This extension was added less than 6 month ago, and so cannot be used on a release
older than Grizzly ( like Folsom ).

Commit of the extension : https://review.openstack.org/#/c/21453/

See https://wiki.openstack.org/wiki/ReleaseNotes/Grizzly#Key_New_Features_2