fix a quirk in cas copier used for copy view then for individual FS copy

If you use the cas copier to copy a view to another view, and reuse the same instance of the cas copier to copy fss, it remembers the view you were copying to, and sets the copied fs's to be in that view. Although it isn't indexing, a subsequent fs_instance.addToIndexes will (if not a subtype of AnnotationBase) add the fs_instance to that last view, rather than the view the cas copier was initially specified with.