DirCacheCheckout is generating names for temporary files. It was not checking
the length of this filenames. It may happen that a generated filename is
longer than 255 chars which causes problems on certain platforms. Make sure
that filenames for temporary files do not exceed 255 chars.
Bug: 508823
Change-Id: I9475c04351ce3faebdc6ad40ea4faa3c326815f4