nfs: disable client side deduplication

The NFS protocol doesn't support deduplication, so turn it off again.

Fixes: ce96e888

 ("Fix nfs4.2 return -EINVAL when do dedupe operation")
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>