Revert "guard against NPE while reading FileTrailer and HFileBlock"

This reverts commit c97905a962.

This is a revert just so I can add the JIRA number to the commit
message.

hbase-server/src/main/java/org/apache/hadoop/hbase/io/hfile/FixedFileTrailer.java

@@ -385,8 +385,7 @@ public class FixedFileTrailer {
       bufferSize = (int) fileSize;
     }
 
-    HFileUtil.seekOnMultipleSources(istream, seekPoint);
+    istream.seek(seekPoint);
-
     ByteBuffer buf = ByteBuffer.allocate(bufferSize);
     istream.readFully(buf.array(), buf.arrayOffset(),
         buf.arrayOffset() + buf.limit());

hbase-server/src/main/java/org/apache/hadoop/hbase/io/hfile/HFileBlock.java

@@ -1450,7 +1450,7 @@ public class HFileBlock implements Cacheable {
       if (!pread && streamLock.tryLock()) {
         // Seek + read. Better for scanning.
         try {
-          HFileUtil.seekOnMultipleSources(istream, fileOffset);
+          istream.seek(fileOffset);
 
           long realOffset = istream.getPos();
           if (realOffset != fileOffset) {

hbase-server/src/main/java/org/apache/hadoop/hbase/io/hfile/HFileUtil.java

@@ -1,43 +0,0 @@
-/**
- * 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.hbase.io.hfile;
-
-import java.io.IOException;
-
-import org.apache.hadoop.fs.FSDataInputStream;
-
-public class HFileUtil {
-
-  /** guards against NullPointer
-   * utility which tries to seek on the DFSIS and will try an alternative source
-   * if the FSDataInputStream throws an NPE HBASE-17501
-   * @param istream
-   * @param offset
-   * @throws IOException
-   */
-  static public void seekOnMultipleSources(FSDataInputStream istream, long offset) throws IOException {
-    try {
-      // attempt to seek inside of current blockReader
-      istream.seek(offset);
-    } catch (NullPointerException e) {
-      // retry the seek on an alternate copy of the data
-      // this can occur if the blockReader on the DFSInputStream is null
-      istream.seekToNewSource(offset);
-    }
-  }
-}