NetConf notification handling

SDN-R is able to handle NetConf notification from connected NetConf Servers. To receive NetConf notifications a mountpoint object (network-topology/netconf/node) must exist in MD-SAL and its (clustered-)connection-status must be "connected".

There are in prinipal two ways to create a mountpoint within MD-SAL:

via a NetConf or RestConf message
via NetConf-Call-Home

The deviceManager component on SDN-R is listening to the connection-status changes for NetConf mountpoints. If the connection-status changes to "connected" the NetConf create-subscription message for netconf notifications is send to the NetConf-server. From now on the NetConf client service is sending NetConf notifications to SDN-R (ODL) devicemanager listener. Every listener on NetConf Notification for this NetConf-Server will trigger the specific handler to process the message.

There are two ODL Listerner interfaces used by devicemanger:

ODL Netconf Client related
- After subscription of NetConf notification stream for mountPoint, using org.opendaylight.yang.gen.v1.urn.ietf.params.xml.ns.netconf.notification._1._0.rev080714.NotificationsService, notifications are forwarded to the listener.
- Related interface class: org.opendaylight.yang.gen.v1.urn.onf.params.xml.ns.yang.microwave.model.rev170324.MicrowaveModelListener extends org.opendaylight.yangtools.yang.binding.NotificationListener extends java.util.EventListener
ODL MDSAL DataTree related
- After regsitration of the listern, all Data Tree changes of related elements are forwarded to the listerner.
- Object id for nodes is specified like this:
  ^{private static final InstanceIdentifier<Node> NETCONF_NODE_TOPO_IID = InstanceIdentifier}
  ^{.create(NetworkTopology.class)}
  ^{.child(Topology.class, new TopologyKey(new TopologyId(TopologyNetconf.QNAME.getLocalName())))}
  ^{.child(Node.class);}
- Related interface class: org.opendaylight.controller.md.sal.binding.api.ClusteredDataTreeChangeListener<Node>

The PNF NetConf Server needs to support capabilites to provide notifications. The related YANG specs are:

<capability>urn:onf:params:xml:ns:yang:microwave-model?module=microwave-model&revision=2017-03-24&features=pure-ethernet,hybrid-microwave</capability>
<capability>urn:ietf:params:xml:ns:netconf:notification:1.0?module=notifications&revision=2008-07-14</capability>

Websocket (WS) based notifications, are provided by different services.

Via port 8185 the ODL MDSAL DataTree offers a WS service for changes in the DataTree, like Creation/Deletion/Change of a mountpoint.
Via port 8085 the