[SCSI] use sysfs configured timeout for EH Start Unit timeout

Use the sysfs configurable timeout when issuing a START_UNIT
command from the scsi error handler. This is needed for devices which
take longer than thirty seconds to respond to the start
unit. The problem was observed when sending a start unit
to a disk array device in an ipr RAID adapter, which results
in the adapter firmware sending potentially multiple commands
to physical devices as a result of this command, which ended
up timing out sometimes. This patch does not change the default
value used for this command.

Signed-off-by: Brian King <brking@linux.vnet.ibm.com>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>