XD-1223 Fix review comments

- Added null check for getMessageBus() method in MessageBus/JobPluginTests.
- Used AlternativeJdkIdGenerator to generate ID for the stream/jobName
  - Also, instead of generating random stream/job name it would be the test method
    name with the generated ID being the suffix to it. One assumption here though
    is that the getStreamName() or getJobName() needs to be called from the actual
    @Test method