HADOOP-14538. Fix TestFilterFileSystem and TestHarFileSystem failures after DistributedFileSystem.append API. Contributed by Lei (Eddy) Xu.

(cherry picked from commit 7ade5124b8b6c52a084ec187c531017eee0f1884)

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/FilterFileSystem.java

@@ -670,4 +670,9 @@ public class FilterFileSystem extends FileSystem {
   public FSDataOutputStreamBuilder createFile(Path path) {
     return fs.createFile(path);
   }
+
+  @Override
+  public FSDataOutputStreamBuilder appendFile(Path path) {
+    return fs.appendFile(path);
+  }
 }

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/HarFileSystem.java

@@ -1273,4 +1273,9 @@ public class HarFileSystem extends FileSystem {
   public FSDataOutputStreamBuilder createFile(Path path) {
     return fs.createFile(path);
   }
+
+  @Override
+  public FSDataOutputStreamBuilder appendFile(Path path) {
+    return fs.appendFile(path);
+  }
 }