orangefs: clean up readdir error handling

Signed-off-by: Mike Marshall <hubcap@omnibond.com>
orangefs: refcount the bufmap structure

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Mike Marshall <hubcap@omnibond.com>
Orangefs: more refcount the bufmap structure

Signed-off-by: Mike Marshall <hubcap@omnibond.com>