Bidirectional plugin doesn't perform unsubscription on device removal

The library has methods that implementes the unsubscribe operation on CB. In particular, the unsubscribe() function at https://github.com/telefonicaid/iotagent-node-lib/blob/master/lib/services/ngsi/subscriptionService.js#L184

function unsubscribe(device, id, callback) {
    ...
    if (device.cbHost) {
        options.uri = 'http://' + device.cbHost + '/v1/unsubscribeContext';
    } else {
        options.uri = 'http://' + config.getConfig().contextBroker.host + ':' + config.getConfig().contextBroker.port +
            '/v1/unsubscribeContext';
    }
...
}

which is called by removeAllSubscriptions() function at https://github.com/telefonicaid/iotagent-node-lib/blob/master/lib/services/devices/deviceService.js#L415:

function removeAllSubscriptions(device, callback) {
    function removeSubscription(subscription, callback) {
        subscriptions.unsubscribe(device, subscription.id, callback);
    }

    if (device.subscriptions) {
        async.map(device.subscriptions, removeSubscription, callback);
    } else {
        callback(null, {});
    }
}

However, nobody in the library is using this method, as can be checked by this search:

• https://github.com/telefonicaid/iotagent-node-lib/search?utf8=%E2%9C%93&q=removeAllSubscriptions&type= (0 hits)

In addition, IOTA agents hasn't any link with this code in the library, I mean nobody using it the IOTA JSON agent:

• https://github.com/telefonicaid/iotagent-json/search?utf8=%E2%9C%93&q=removeAllSubscriptions&type= (0 hits)
• https://github.com/telefonicaid/iotagent-json/search?utf8=%E2%9C%93&q=unsubscribe&type= (1 hits in no test code but related with MQTT)

and nobody using in the IOTA UL agent:

• https://github.com/telefonicaid/iotagent-ul/search?utf8=%E2%9C%93&q=removeAllSubscriptions&type= (0 hits)
• https://github.com/telefonicaid/iotagent-ul/search?utf8=%E2%9C%93&q=unsubscribe&type= (1 hit in no test code but related with MQTT)

If my theory confirms (I may be wrong) it seems that unsubcription code in the library is dead code. As a consecuence, subscriptions are not correctly cleaned up when devices are deleted by API, leaving dirty stuff in CB.

Start in lib/services/ngsi/subscriptionService.js at unsubscribe() and lib/services/devices/deviceService.js at removeAllSubscriptions(). Trace device-removal callers and search the related agent repositories to verify whether cleanup is connected. Done means device deletion triggers the intended Context Broker unsubscription, with tests covering the cleanup path.