NFSv4: Add support for delegated atime and mtime attributes

Ensure that we update the mtime and atime correctly when we read
or write data to the file and when we truncate. Let the server manage
ctime on other attribute updates.

Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
Signed-off-by: Lance Shelton <lance.shelton@hammerspace.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>