NFSv4.1: Kill nfs4_ds_disconnect()

There is nothing to prevent another thread from dereferencing ds->ds_clp
during or after the call to nfs4_ds_disconnect(), and Oopsing due to the
resulting NULL pointer.

Instead, we should just rely on filelayout_mark_devid_invalid() to keep
us out of trouble by avoiding that deviceid.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

fs/nfs/nfs4filelayout.c

@@ -207,7 +207,6 @@ static int filelayout_async_handle_error(struct rpc_task *task,
 		clear_bit(NFS_INO_LAYOUTCOMMIT, &NFS_I(inode)->flags);
 		_pnfs_return_layout(inode);
 		rpc_wake_up(&tbl->slot_tbl_waitq);
-		nfs4_ds_disconnect(clp);
 		/* fall through */
 	default:
 reset: