
The DVO locking policy is a little bit broken.  DVO currently
(2009.08.10) requires that users have write access to files because
the code does not distinguish well cases where read-only (soft locks)
are used vs cases of read/write (hard locks) are needed.

locks set in DVO:

dvo_catalog_lock -- on catalog open & catalog create (all files for
		    split mode)

gfits_db_lock -- on photcode table read/write and dvo_image_lock

