[SCSI] sd: Avoid remapping bad reference tags

It does not make sense to translate ref tags with unexpected values.
Instead we simply ignore them and let the upper layers catch the
problem. Ref tags that contain the expected value are still remapped.

Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>