Don't return deleted docs for conflicts

Don't return deleted docs for conflict resolution. Deleted documents are not normally
in conflict, in CDTDatastore conflict resolution does not return deleted leaves.

Modify test which expects a winning rev to be deleted to expect no rev provided as
a conflict is deleted.
Use the same terminology as the other method: "Returns the leaf revisions", and put "this is the same as calling..." in the next para.

Similarly make the two @return statements the same - in this case I think yours is better