scsi_dh_alua: call alua_rtpg() if stpg fails

If the call to SET TARGET PORT GROUPS fails we have no idea what
state the array is left in, so we need to issue a call to
REPORT TARGET PORT GROUPS in these cases.
Reviewed-by: Bart Van Assche <bart.vanassche@sandisk.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

BugLink: http://bugs.launchpad.net/bugs/1567602

(cherry-picked from commit dd5cc408)
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>
Acked-by: Brad Figg <brad.figg@canonical.com>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>

drivers/scsi/device_handler/scsi_dh_alua.c

@@ -674,6 +674,8 @@ static int alua_activate(struct scsi_device *sdev,
 		h->flags |= ALUA_OPTIMIZE_STPG;
 
 	err = alua_stpg(sdev, h);
+	if (err == SCSI_DH_RETRY)
+		err = alua_rtpg(sdev, h, 1);
 out:
 	if (fn)
 		fn(data, err);