minor tweak to patch for MAPREDUCE-4511 (Add IFile readahead) to avoid use of interface HasFileDescriptor, which doesn't exist until 1.2

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-1.1@1392182 13f79535-47bb-0310-9956-ffa450edef68

src/mapred/org/apache/hadoop/mapred/IFileInputStream.java

@@ -29,7 +29,6 @@ import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
 import org.apache.hadoop.fs.ChecksumException;
 import org.apache.hadoop.fs.FSDataInputStream;
-import org.apache.hadoop.fs.HasFileDescriptor;
 import org.apache.hadoop.io.IOUtils;
 import org.apache.hadoop.io.ReadaheadPool;
 import org.apache.hadoop.io.ReadaheadPool.ReadaheadRequest;
@@ -101,9 +100,7 @@ class IFileInputStream extends InputStream {
   private static FileDescriptor getFileDescriptorIfAvail(InputStream in) {
     FileDescriptor fd = null;
     try {
-      if (in instanceof HasFileDescriptor) {
-        fd = ((HasFileDescriptor)in).getFileDescriptor();
-      } else if (in instanceof FileInputStream) {
+      if (in instanceof FileInputStream) {
         fd = ((FileInputStream)in).getFD();
       }
     } catch (IOException e) {