HADOOP-16045. Don't run TestDU on Windows. Contributed by Lukas Majercak.

(cherry picked from commit 35fa3bd685605d8b3639e6c5cbe83cd9acd8cbe7)

hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/fs/TestDU.java

@@ -17,10 +17,12 @@
  */
 package org.apache.hadoop.fs;
 
+import org.apache.hadoop.util.Shell;
 import org.junit.After;
 import org.junit.Before;
 import org.junit.Test;
 import static org.junit.Assert.*;
+import static org.junit.Assume.assumeFalse;
 
 import java.io.File;
 import java.io.IOException;
@@ -37,6 +39,7 @@ public class TestDU {
 
   @Before
   public void setUp() {
+    assumeFalse(Shell.WINDOWS);
     FileUtil.fullyDelete(DU_DIR);
     assertTrue(DU_DIR.mkdirs());
   }