OAK-1817 - NPE in MarkSweepGarbageCollector.saveBatchToFile during Datastore GC with FileDataStore

Modified the testcase which reproduces the original issue. Looks like creating large number of blob causes issue with blob ref accounting logic

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1596474 13f79535-47bb-0310-9956-ffa450edef68