scsi: ILLEGAL REQUEST + ASC==27 => target failure

ASC 0x27 is "WRITE PROTECTED". This error code is returned e.g.  by
Fujitsu ETERNUS systems under certain conditions for WRITE SAME 16
commands with UNMAP bit set. It should not be treated as a path
error. In general, it makes sense to assume that being write protected
is a target rather than a path property.

Signed-off-by: Martin Wilck <mwilck@suse.com>
Acked-by: Lee Duncan <lduncan@suse.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>