OPENDJ-2460: fix pluggable backend unit tests This was evil. TestNG has a bug which prevents method dependencies from working with inheritance. When looking to see if another test method has already completed it sometimes looks in the wrong sub-class instance, when it should look in the current sub-class instance I tried to refactor the JE/PDB tests to use @Factory for creating test instances (one for PDB one for JE), but both instances end up being invoked in parallel. In order to preserve the ordering I tried using the "priority" @Test attribute, but it did not work. I reordered the test methods and ran them sequentially, but TestNG ignores the declaration order and just runs them in alphabetical order. Finally, I refactored the tests so that they have no side-effects and can be run in any order, which was probably the right thing to do anyway.

Add tests for pluggable JEBackend It's disabled at the moment because the rebuild index test is hanging.