Automatic merge from submit-queue
volume/flocker: plug time.Ticker resource leak
This commit ensures that `flockerMounter.updateDatasetPrimary` does not leak
running `time.Ticker` instances. Upon termination of the consuming routine, we
stop the tickers.
```release-note
* flockerMounter.updateDatasetPrimary no longer leaks running time.Ticker instances.
Upon termination of the consuming routine, we stop the tickers.
```