pnfs-obj: pNFS errors are communicated on iodata->pnfs_error

pnfs-obj: pNFS errors are communicated on iodata->pnfs_error

commit 5c0b4129c07b902b27d3f3ebc087757f534a3abd upstream.

Some time along the way pNFS IO errors were switched to
communicate with a special iodata->pnfs_error member instead
of the regular RPC members. But objlayout was not switched
over.

Fix that!
Without this fix any IO error is hanged, because IO is not
switched to MDS and pages are never cleared or read.

[Applies to 3.2.0. Same bug different patch for 3.1/0 Kernels]
Signed-off-by: Boaz Harrosh <bharrosh@panasas.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>