HADOOP-15936. [JDK 11] MiniDFSClusterManager & MiniHadoopClusterManager compilation fails due to the usage of '_' as identifier. Contributed by Zsolt Venczel.

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/test/MiniDFSClusterManager.java

@@ -127,7 +127,7 @@ public class MiniDFSClusterManager {
           LOG.info("Cluster is no longer up, exiting");
           return;
         }
-      } catch (InterruptedException _) {
+      } catch (InterruptedException e) {
         // nothing
       }
     }

hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-jobclient/src/test/java/org/apache/hadoop/mapreduce/MiniHadoopClusterManager.java

@@ -137,7 +137,7 @@ public class MiniHadoopClusterManager {
     while (true) {
       try {
         Thread.sleep(1000 * 60);
-      } catch (InterruptedException _) {
+      } catch (InterruptedException e) {
         // nothing
       }
     }