Merge pull request #232 from markhamstra/FiniteWait

jobWaiter.synchronized before jobWaiter.wait

...else ``IllegalMonitorStateException`` in ``SimpleFutureAction#ready``.

(cherry picked from commit 078049877e123fe7e4c4553e36055de572cab7c4)
Signed-off-by: Reynold Xin <rxin@apache.org>