HDFS-14367. EC: Parameter maxPoolSize in striped reconstruct thread pool isn't affecting number of threads. Contributed by Guo Lei.

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/erasurecode/ErasureCodingWorker.java

@@ -106,7 +106,7 @@ public final class ErasureCodingWorker {
   private void initializeStripedBlkReconstructionThreadPool(int numThreads) {
     LOG.debug("Using striped block reconstruction; pool threads={}",
         numThreads);
-    stripedReconstructionPool = DFSUtilClient.getThreadPoolExecutor(2,
+    stripedReconstructionPool = DFSUtilClient.getThreadPoolExecutor(numThreads,
         numThreads, 60, new LinkedBlockingQueue<>(),
         "StripedBlockReconstruction-", false);
     stripedReconstructionPool.allowCoreThreadTimeOut(true);