NFSv4: Fix a cache validation bug which causes getcwd() to return ENOENT

Changeset a65318bf

 (NFSv4: Simplify some
cache consistency post-op GETATTRs) incorrectly changed the getattr
bitmap for readdir().
This causes the readdir() function to fail to return a
fileid/inode number, which again exposed a bug in the NFS readdir code that
causes spurious ENOENT errors to appear in applications (see
http://bugzilla.kernel.org/show_bug.cgi?id=14541).

The immediate band aid is to revert the incorrect bitmap change, but more
long term, we should change the NFS readdir code to cope with the
fact that NFSv4 servers are not required to support fileids/inode numbers.

Reported-by: Daniel J Blueman <daniel.blueman@gmail.com>
Cc: stable@kernel.org
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>