TTL Task cannot be canceled if the TiDB lost heartbeat

## Bug Report

```go
// checkInvalidTask removes the task whose owner is not myself or which has disappeared
func (m *taskManager) checkInvalidTask(se session.Session) {
...

		if t.OwnerID == m.id {
			ownRunningTask = append(ownRunningTask, task)
		}
	}

	m.runningTasks = ownRunningTask
}
```

If the `t.OwnerID != m.id`, the task should also be canceled and release the worker.