Notify all metric reporters when metric registry has been changed

With existing implementation, it is difficult to notify the
metric reports on metric registry changes. With this commit,
we can spontaneously notify all reporters about the metric
registry changes, so that newly added metrics can be automatically
reported to third party monitoring system.

Change-Id: I1273194553900f6bb03e2ef6bb1b54838af1da00
diff --git a/apps/cpman/app/src/test/java/org/onosproject/cpman/rest/ControlMetricsCollectorResourceTest.java b/apps/cpman/app/src/test/java/org/onosproject/cpman/rest/ControlMetricsCollectorResourceTest.java
index 727d1df..effb3de 100644
--- a/apps/cpman/app/src/test/java/org/onosproject/cpman/rest/ControlMetricsCollectorResourceTest.java
+++ b/apps/cpman/app/src/test/java/org/onosproject/cpman/rest/ControlMetricsCollectorResourceTest.java
@@ -28,6 +28,7 @@
 import org.junit.Test;
 import org.onlab.metrics.MetricsComponent;
 import org.onlab.metrics.MetricsFeature;
+import org.onlab.metrics.MetricsReporter;
 import org.onlab.metrics.MetricsService;
 import org.onlab.osgi.ServiceDirectory;
 import org.onlab.osgi.TestServiceDirectory;
@@ -220,6 +221,18 @@
         }
 
         @Override
+        public void registerReporter(MetricsReporter reporter) {
+        }
+
+        @Override
+        public void unregisterReporter(MetricsReporter reporter) {
+        }
+
+        @Override
+        public void notifyReporters() {
+        }
+
+        @Override
         public boolean removeMetric(MetricsComponent component,
                                     MetricsFeature feature, String metricName) {
             return false;