Separate out LockChangeListener from NetconfDeviceSalFacade

LockChangeListener maintains a single boolean in NetconfDeviceDataBroker and AbstractNetconfDataTreeService. This drives the behaviour of NetconfDataTreeService and NetconfDeviceDataBroker transactions. Unfortunately, this implies sal-netconf-connector has a strong tie with netconf topology – which is not appropriate.

Split the logic of maintaining this bit into netconf.topology.spi while enforcement remains in sal-netconf-connector – providing another step in making sal-netconf-connector topology-independent.