[SCSI] Wrong size information for devices with disabled read access

When accessing a device with disabled read access the capacity is set
randomly to 1GB. This makes it impossible to userspace tools to detect
invalid device capacities.

Signed-off-by: Mike Anderson <andmike@us.ibm.com>
Acked-by: Chris Mason <mason@suse.com>
Signed-off-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>