[SPARK-13468][WEB UI] Fix a corner case where the Stage UI page should show DAG but it doesn't show

When uses clicks more than one time on any stage in the DAG graph on the *Job* web UI page, many new *Stage* web UI pages are opened, but only half of their DAG graphs are expanded.

After this PR's fix, every newly opened *Stage* page's DAG graph is expanded.

Before:
![](https://cloud.githubusercontent.com/assets/15843379/13279144/74808e86-db10-11e5-8514-cecf31af8908.png)

After:
![](https://cloud.githubusercontent.com/assets/15843379/13279145/77ca5dec-db10-11e5-9457-8e1985461328.png)

## What changes were proposed in this pull request?

- Removed the `expandDagViz` parameter for _Stage_ page and related codes
- Added a `onclick` function setting `expandDagVizArrowKey(false)` as `true`

## How was this patch tested?

Manual tests (with this fix) to verified this fix work:
- clicked many times on _Job_ Page's DAG Graph → each newly opened Stage page's DAG graph is expanded

Manual tests (with this fix) to verified this fix do not break features we already had:
- refreshed many times for a same _Stage_ page (whose DAG already expanded) → DAG remained expanded upon every refresh
- refreshed many times for a same _Stage_ page (whose DAG unexpanded) → DAG remained unexpanded upon every refresh
- refreshed many times for a same _Job_ page (whose DAG already expanded) → DAG remained expanded upon every refresh
- refreshed many times for a same _Job_ page (whose DAG unexpanded) → DAG remained unexpanded upon every refresh

Author: Liwei Lin <proflin.me@gmail.com>

Closes #11368 from proflin/SPARK-13468.