[SCSI] sr: fix sr_drive_status handling when initialization required

An sr device that reports sense data with SK/ASC/ASCQ of 2/4/2 (Not ready,
Logical unit not ready, Initializing command required) will be handled
in sr_drive_status as (2/4/!1) and assumed to be a 'format in progress'
which returns CDS_DISC_OK.  The drive will not be made ready in this case.

Prior to 210ba1d1

 sr_drive_status would
have returned CDS_TRAY_OPEN and this results in an START_STOP_UNIT to
close the tray, which resolves the initialization requirement.

This patch adds handling for SK/ASC/ASCQ of 2/4/2 where it will return
CDS_TRAY_OPEN as a means of triggering a START_STOP_UNIT.

This issue is seen on the IBM POWER platform when using a file-backed,
virtual optical device.  The device does not support media queries
through the Get Event Status Notification command which could otherwise
trigger a START_STOP_UNIT call to close an open tray.

Signed-off-by: Robert Jennings <rcj@linux.vnet.ibm.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>