I have it working now, reverting back to using this worked for me:
@RunWith(com.carrotsearch.randomizedtesting.RandomizedRunner.class)
@ContextConfiguration(classes = { SearchTestSpringConfig.class } )
@ThreadLeakScope(ThreadLeakScope.Scope.NONE)
public class SearchIT extends ESTestCase {
(rather than using ESIntegTestCase).
That was harder than it should have been!