[SCSI] fix memory leak in scsi_report_lun_scan

This patch (as1333) fixes a bug in scsi_report_lun_scan().  If a
newly-allocated device can't be used, it should be deleted.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>