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/gangliametrics/src/test/java/org/onosproject/gangliametrics/GangliaMetricsReporterTest.java b/apps/gangliametrics/src/test/java/org/onosproject/gangliametrics/GangliaMetricsReporterTest.java
index d8dd49b..c911a8e 100644
--- a/apps/gangliametrics/src/test/java/org/onosproject/gangliametrics/GangliaMetricsReporterTest.java
+++ b/apps/gangliametrics/src/test/java/org/onosproject/gangliametrics/GangliaMetricsReporterTest.java
@@ -28,7 +28,7 @@
  */
 public class GangliaMetricsReporterTest {
 
-    private GangliaMetricsReporter gmr;
+    private DefaultGangliaMetricsReporter gmr;
 
     private static final String METRIC_NAME1 = "consistentMap.onos-app-ids.putIfAbsent";
     private static final String METRIC_NAME2 = "consistentMap.onos-hosts.entrySet";
@@ -45,7 +45,7 @@
      */
     @Before
     public void setUp() {
-        gmr = new GangliaMetricsReporter();
+        gmr = new DefaultGangliaMetricsReporter();
     }
 
     /**