scsi_dh_alua: Enable STPG for unavailable ports

commit e47f8976 upstream.

A quote from SPC-4: "While in the unavailable primary target port
asymmetric access state, the device server shall support those of
the following commands that it supports while in the active/optimized
state: [ ... ] d) SET TARGET PORT GROUPS; [ ... ]". Hence enable
sending STPG to a target port group that is in the unavailable state.
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: Mike Christie <michaelc@cs.wisc.edu>
Acked-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

drivers/scsi/device_handler/scsi_dh_alua.c

@@ -578,8 +578,7 @@ static int alua_rtpg(struct scsi_device *sdev, struct alua_dh_data *h)
 		h->state = TPGS_STATE_STANDBY;
 		break;
 	case TPGS_STATE_OFFLINE:
-	case TPGS_STATE_UNAVAILABLE:
-		/* Path unusable for unavailable/offline */
+		/* Path unusable */
 		err = SCSI_DH_DEV_OFFLINED;
 		break;
 	default: