Track attached SCSI devices and update the 'access_state' field whenever
an ALUA state change has been detected.
Signed-off-by: Hannes Reinecke <hare@suse.de> Reviewed-by: Bart Van Assche <bart.vanassche@sandisk.com> Reviewed-by: Ewan Milne <emilne@redhat.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de> Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>