Bug 4094: Fix DCNs on initial registration

Bug 4094: Fix DCNs on initial registration

For DataChangeListener, I modified the code to use a
ResolveDataChangeEventsTask to resolve the initial changed event. It
was noted in Bug 4094 to read the registration path up to the first
wildcard. However this did not work. ResolveDataChangeEventsTask
expects the candidate root path and "after" data to be the tree root
to match the structure of the ListenerTree. When a transaction is
committed, the resulting DataTreeCandidate always points to the root.
So I had to read the root path in ShardDataTree. I could've optimized
for non-wildcarded path registrations but I think wildcarded path
registrations will be the norm anyway.

I added a new method, notifyOfInitialData, in ShardDataTree. Because I
had to create a new ListenerTree with the single registration, I
needed to know the path and scope of the original registration so I
changed several method signatures from the general ListenerRegistration
to the specific DataChangeListenerRegistration which provides access to
the path and scope. However we also have an actor class by that name so
to avoid confusion I renamed the actor class to
DataChangeListenerRegistrationActor.

DataTreeChangeListener was implemented similarly.

Change-Id: I0ab88d0991761c058b6af81d6d26402ff370b78e
Signed-off-by: Tom Pantelis <tpanteli@brocade.com>