Fix for bug #5790 - samba returns STATUS_OBJECT_NAME_NOT_FOUND on set file disposition call.
This was my fault. I use a singleton cache (positive and negative) to speed up pathname based
qfileinfo/setfileinfo lookups for alternate fsp's open on the same path. I only invalidated the
negative cache on adding a new file fsp, as I incorrectly imagined the new fsp was put at the *end* of
the open files list. DLIST_ADD puts it at the start, meaning any subsequent open wasn't seen once the
cache was set. Doh !
Jeremy.