[Umbrella] Migrate junit tests from JUnit 3 to JUnit 4

OOZIE-783 upgraded JUnit 3 to JUnit 4 years ago, but most of out unit tests still use JUnit 3 style.

The following counting is not perfect, but shows the approximate numbers:

$ find . -name "Test*.java" | wc -l
     491
$ find . -name "Test*.java" | xargs grep 'extends.*TestCase' -l | wc -l
     346

Although there are ways to automagically convert the tests, I don't think we can skip the manual work.

I open this umbrella jira (similarly to OOZIE-3111) so at least we are aware of the problem. We need to solve it in batches.