Bug 8231: Fix testChangeListenerRegistration failure

Bug 8231: Fix testChangeListenerRegistration failure

As described in Bug 8231, the sharing of the ListenerTree between the
ShardDataTree and the ShardDataTreeNotificationPublisherActor is
problematic. Therefore the ListenerTree (wrapped by the
DefaultShardDataTreeChangeListenerPublisher) is now owned by the
ShardDataTreeNotificationPublisherActor. On registration, a RegisterListener
messages is sent to the ShardDataTreeNotificationPublisherActor to perform
the on-boarding of the new listener, ie it atomically generates and sends
the initial notification and then adds the listener to the ListenerTree.

This change necessitated some refactoring of the DataChangeListenerSupport
class et al wrt to how the ListenerRegistration is handled. Prior the
ListenerRegistration was passed on creation of the registration actor. This
is now done indirectly by sending a SetRegistration message to the
registration actor via a Consumer callback passed in the RegisterListener
message. When the ListenerRegistration is obtained by the
ShardDataChangePublisherActor, it invokes the Consumer callback.

When a registration is initially delayed due to no leader, the
DelayedListenerRegistration is sent to the registration actor. When the
leader is elected later on, the actual ListenerRegistration is sent and
replaces the DelayedListenerRegistration.

The DOMDataTreeChangeListener registration classes were changed/refactored
similarly.

In addition, the 2 specific registration actor classes were replaced by a
generic reusable DataTreeNotificationListenerRegistrationActor that handles
both listener types. Also the 2 CloseData*ListenerRegistration and
CloseData*ListenerRegistrationReply messages were consolidated.

Change-Id: I79ac76b8044609351e5dd8367b691b589ea35075
Signed-off-by: Tom Pantelis <tompantelis@gmail.com>