[OpenAFS] Cache file status after Network error

[Tom Fitzgerald]

> Between the cleanup and the close file access will continue if the
> file has been memory mapped.  The cache manager cannot discard the
> writes because doing so would corrupt any memory mapped regions.

What happens to processes with memory-mapped local files if the
local disk fails and starts returning I/O errors when dirty
pages are flushed?  There's a good argument for duplicating this
behavior.  (Programs certainly can't expect more consistency from
a network filesystem than they get from a local filesystem, in
the presence of hardware failures.)