XD-2333 Add Kafka integration test

- Add kafka test support class that checks for kafka server availablity
  on localhost
- This uses zk server available on default connect string `localhost:2181`
- Add test for verifying kafka source and sink having both the source/sink
  on the same test case will make sure the topic that gets the data by
  kafka sink is actually read by kafka source
- Handle Zk connect exceptions
- Fix create/delete topic in Before/After
- Remove explicit sleep by setting kafka source consumer
  timeout to -1 (blocking)
- Fix import statements