scsi: scsi_dh_alua: Set 'transitioning' state on Unit Attention

scsi: scsi_dh_alua: Set 'transitioning' state on Unit Attention

We should be setting the 'transitioning' ALUA state once we get a Unit
Attention indicating the array is in transitioning.  There are arrays which
cannot respond to an RTPG while in transitioning, and others have issues
correctly reporting the state.  So better to set the state during Unit
Attention handling and wait for TUR / RTPG to run its course.

Link: https://lore.kernel.org/r/20200930080256.90964-4-hare@suse.de
Reviewed-by: Ewan D. Milne <emilne@redhat.com>
Signed-off-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>