fixes #2747

WriteBehindManager start() and stop() methods are enhanced.added test method.
Although checkstyle won't complain about 0, 1 as magic number. I personally would introduce a constant for readability. You don't need to change it, but think about it.

It is a shame that java doesn't supported named arguments:

```
scheduleAtFixedRate(storeWorked,initialDelay:1, period:1, unit:TimeUint.SECONDS)
```
Then at least the code becomes self explaining.