GUI is messed up when there're job running.

issue addressed in [ZEPPELIN-131](https://zeppelin-project.atlassian.net/browse/ZEPPELIN-131)

* [x] fix zeppelin is keep loading the same job whatever i clicked, when a job is running.
* [x] if some job is in queue, zeppelin display it as READY, even if i click RUN and job is submitted.
* [x] Change default job scheduler from FIFO to PARALLEL
* [x] js polling routine starts everytime new job opened, but never finishes even if job chaning, result multiple routine is keep polling job