MAPREDUCE-7136. TestMRAppMetrics should shutdown DefaultMetricsSystem after completion. Contributed by Oleksandr Shevchenko

hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/test/java/org/apache/hadoop/mapreduce/v2/app/metrics/TestMRAppMetrics.java

@@ -24,12 +24,19 @@ import org.apache.hadoop.metrics2.MetricsRecordBuilder;
 
 import static org.apache.hadoop.test.MetricsAsserts.*;
 
+import org.apache.hadoop.metrics2.lib.DefaultMetricsSystem;
+import org.junit.After;
 import org.junit.Test;
 
 import static org.mockito.Mockito.*;
 
 public class TestMRAppMetrics {
 
+  @After
+  public void tearDown() {
+    DefaultMetricsSystem.shutdown();
+  }
+
   @Test public void testNames() {
     Job job = mock(Job.class);
     Task mapTask = mock(Task.class);