When job is re-submitted, previous status is still there until job is actually started and become RUNNING.
Other thread could not distinguash between finished job and re-submitted/queued job.

This commit make before job re-submit, set status READY (from previous status like FINISHED, ERRROR, ABORTED).
So we can finally remove error prone constant time waiting statement from test.
Merge pull request #22 from NFLabs/make_session_manager_test_more_predictable

Fixing ZQLSessionManagerTest failure
Make sure history created before status changed to FINISHED.
Merge pull request #23 from NFLabs/make_session_manager_test_more_predictable

make JobManagerTest more predictable
Merge branch 'master' into zan