scsi: scsi_dh_alua: fix missing kref_put() in alua_rtpg_work()

Reference count of pg leaks in alua_rtpg_work() since kref_put() is not
called to decrease the reference count of pg when the condition
pg->rtpg_sdev==NULL satisfied (actually it is easy to satisfy), it would
cause memory of pg leakage.
Signed-off-by: Ntang.junhui <tang.junhui@zte.com.cn>
Cc: <stable@vger.kernel.org>
Reviewed-by: NHannes Reinecke <hare@suse.com>
Signed-off-by: NMartin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/device_handler/scsi_dh_alua.c

@@ -793,6 +793,7 @@ static void alua_rtpg_work(struct work_struct *work)
 		WARN_ON(pg->flags & ALUA_PG_RUN_RTPG);
 		WARN_ON(pg->flags & ALUA_PG_RUN_STPG);
 		spin_unlock_irqrestore(&pg->lock, flags);
+		kref_put(&pg->kref, release_port_group);
 		return;
 	}
 	if (pg->flags & ALUA_SYNC_STPG)