Fixing findbugs and license issues related to:

HADOOP-15703. ABFS - Implement client-side throttling.
Contributed by Sneha Varma and Thomas Marquardt.

hadoop-tools/hadoop-azure/src/main/java/org/apache/hadoop/fs/azurebfs/services/AbfsClientThrottlingIntercept.java

@@ -46,8 +46,6 @@ public final class AbfsClientThrottlingIntercept {
   private AbfsClientThrottlingIntercept() {
     readThrottler = new AbfsClientThrottlingAnalyzer("read");
     writeThrottler = new AbfsClientThrottlingAnalyzer("write");
-    isAutoThrottlingEnabled = true;
-    LOG.debug("Client-side throttling is enabled for the ABFS file system.");
   }
 
   public static synchronized void initializeSingleton(boolean isAutoThrottlingEnabled) {
@@ -56,6 +54,8 @@ public final class AbfsClientThrottlingIntercept {
     }
     if (singleton == null) {
       singleton = new AbfsClientThrottlingIntercept();
+      isAutoThrottlingEnabled = true;
+      LOG.debug("Client-side throttling is enabled for the ABFS file system.");
     }
   }
 

hadoop-tools/hadoop-azure/src/test/java/org/apache/hadoop/fs/azurebfs/services/TestAbfsClientThrottlingAnalyzer.java

@@ -1,3 +1,21 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
 package org.apache.hadoop.fs.azurebfs.services;
 
 import org.apache.hadoop.fs.contract.ContractTestUtils;