[SCSI] Correctly set the scsi host/msg/status bytes

Resubmitting as my previous post had format issues and did not go llinux-scsi.
This patch changes the function to set_msg_byte, set_host_byte and
set_driver_byte to correctly set the corresponding bytes appropriately.

It will reset the original setting and correctly set it to the new value.  The
previous OR operation does not always set it back to new value. Look at patch
2/2 for an example.

Signed-off-by: Babu Moger <babu.moger@netapp.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>