Add missing @Test annotation. @Ignore non-working test.
Do dead node recovery and activity timestamping at correct period.

ExecutorDao was doing dead node recovery at every tick(), because nextUpdate was
initally set to Unix epoch and increased small duration at every tick.
Fix and enable test doesNotWakeUpRunningWorkflow
Always wait at least keepaliveSeconds for next update.
Use DateTime.now() instead of new DateTime()
Merge pull request #21 from NitorCreations/improve-tests

Improve tests