HDFS-12470. DiskBalancer: Some tests create plan files under system directory. Contributed by Hanisha Koneru.

(cherry picked from commit a2dcba18531c6fa4b76325f5132773f12ddfc6d5)

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/diskbalancer/command/TestDiskBalancerCommand.java

@@ -476,9 +476,12 @@ public class TestDiskBalancerCommand {
   public void testPlanJsonNode() throws Exception {
     final String planArg = String.format("-%s %s", PLAN,
         "a87654a9-54c7-4693-8dd9-c9c7021dc340");
+    final Path testPath = new Path(
+        PathUtils.getTestPath(getClass()),
+        GenericTestUtils.getMethodName());
     final String cmdLine = String
         .format(
-            "hdfs diskbalancer %s", planArg);
+            "hdfs diskbalancer -out %s %s", testPath, planArg);
     runCommand(cmdLine);
   }