added function entry_invis() in addition to entry_has_expired(). entry_invis() returns true if entry_has_expired() or for negative entries. the is_negative flag is set for negative entries (defined as having entry->attributes == NULL), and returned by nfs41_name_cache_lookup(). when nfs41_lookup() sees this flag set, it returns the status without attempting to do any more lookups
Signed-off-by: Casey Bodley <cbodley@umich.edu>
