Netconf testtool does not support nc-notifications model

Testtool is unable to deal proper with notifications described in: https://tools.ietf.org/html/rfc5277#section-2. It does not support nc-notification model and therefore invoked create-subscription operation do nothing. On the other hands all registered streams should be included in nc-notification model.

Depends on NETCONF-307 it is not possible test notifications in odl-clustered-topology in the following way: The user registers particular notification listeners and invokes create-subscription (notification stream is started) but if master node is down and new connection is initiated (new session) device streams are terminated. We have to invoke create-subscription with proper streams additionally by cluster (for user it must by hidden), but we lack stream name information, which must be saved from nc-notification model before master is down.