[SCSI] Ensure discard failure gets treated as a target problem
The error reported up the stack for a discard failure did not clearly
indicate that the command was processed and subsequently failed by the
target device.
Return -EREMOTEIO so multipathing does not classify this condition as a
path failure.
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com> Acked-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: James Bottomley <JBottomley@Parallels.com>