[SCSI] scsi_dh_alua: Re-enable STPG for unavailable ports

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 re-enable
sending STPG to a target port group that is in the unavailable state.
Signed-off-by: NBart Van Assche <bvanassche@acm.org>
Reviewed-by: Babu Moger <babu.moger@netapp.com> 
Signed-off-by: NJames Bottomley <JBottomley@Parallels.com>

drivers/scsi/device_handler/scsi_dh_alua.c

@@ -742,9 +742,9 @@ static int alua_activate(struct scsi_device *sdev,
 				stpg = 0;
 			break;
 		case TPGS_STATE_STANDBY:
+		case TPGS_STATE_UNAVAILABLE:
 			stpg = 1;
 			break;
-		case TPGS_STATE_UNAVAILABLE:
 		case TPGS_STATE_OFFLINE:
 			err = SCSI_DH_IO;
 			break;