continuationToken is not returned from a get_metric_details call in the metric_api

[mdennehy]

For example, we have to do this to get more than the limit of results:

    api_response = metric_api.get_metric_details(metric, l=1000)
    data = json.loads(client.last_response.data)
    if len(api_response.hosts) == 1000:
        cursor = data['continuationToken']

This obviously isn't great, because we shouldn't be diving that deep into the client structure for a result from an API call.