Additional unit tests for AbstractOozieJobsTask

[misolt]

The lines:

  // AbstractOozieJobsTask.java
  if (record[i] != null && record[i] instanceof List) {
    // write Actions arrays as json string in csv
    record[i] = objectMapper.writeValueAsString(record[i]);

show up as covered in jacoco, but after removing them the tests still pass.

Add class-specific tests for AbstractOozieJobsTask to ensure that validation is correct.