Fix for HADOOP-57. Permit listing of "/" in dfs. With help from Mahadev konar.

git-svn-id: https://svn.apache.org/repos/asf/lucene/hadoop/trunk@384019 13f79535-47bb-0310-9956-ffa450edef68

src/java/org/apache/hadoop/dfs/DistributedFileSystem.java

@@ -266,6 +266,9 @@ public class DistributedFileSystem extends FileSystem {
         path.append(DFSFile.DFS_FILE_SEPARATOR);
         path.append(l.get(i));
       }
+      if (f.isAbsolute() && path.length() == 0) {
+        path.append(DFSFile.DFS_FILE_SEPARATOR);
+      }
       return path.toString();
     }