Fix bug in compressed binary doc values bulk decoding.

Reuse firstBlockId as blockId on first iteration.

Author: martijnvg

server/src/main/java/org/elasticsearch/index/codec/tsdb/es819/ES819TSDBDocValuesProducer.java

@@ -617,7 +617,7 @@ void decodeBulk(int numBlocks, int firstDoc, int count, BlockLoader.SingletonByt
             byte[] bytes = new byte[bufferSize];
 
             while (remainingCount > 0) {
-                long blockId = findAndUpdateBlockByScanning(nextDoc);
+                long blockId = remainingCount == count ? firstBlockId : findAndUpdateBlockByScanning(nextDoc);
                 int numDocsInBlock = (int) (limitDocNumForBlock - startDocNumForBlock);
                 int idxFirstDocInBlock = (int) (nextDoc - startDocNumForBlock);
                 int countInBlock = Math.min(numDocsInBlock - idxFirstDocInBlock, remainingCount);