[SCSI] sd: Quiesce mode sense error messages

Messages about discovered disk properties are only printed once unless
they are found to have changed. Errors encountered during mode sense,
however, are printed every time we revalidate.

Quiesce mode sense errors so they are only printed during the first
scan.

[jejb: checkpatch fixes]
Bugzilla: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=733565
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>