We're already invalidating the data cache, and setting the new change
attribute. Since directories don't care about the i_size field, there
is no need to be forcing any extra revalidation of the page cache.

We do keep the NFS_INO_INVALID_ATTR flag, in order to force an
attribute cache revalidation on stat() calls since we do not
update the mtime and ctime fields.
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>