Bug fix: Graphite reporter

- It never changes report period bacause of Default config
- TODO: implement retriever and add some function

Change-Id: I578c7fedefbe76f265dd43091588dd19d541ffa1

@@ -127,7 +127,7 @@ public class DefaultGraphiteMetricsReporter implements GraphiteMetricsReporter {
         graphiteReporter = buildReporter(graphite);
 
         try {
-            graphiteReporter.start(DEFAULT_REPORT_PERIOD, REPORT_TIME_UNIT);
+            graphiteReporter.start(reportPeriod, REPORT_TIME_UNIT);
         } catch (Exception e) {
             log.error("Errors during reporting to graphite, msg: {}" + e.getMessage());
         }
@@ -154,7 +154,7 @@ public class DefaultGraphiteMetricsReporter implements GraphiteMetricsReporter {
         graphiteReporter = buildReporter(graphite);
 
         try {
-            graphiteReporter.start(DEFAULT_REPORT_PERIOD, REPORT_TIME_UNIT);
+            graphiteReporter.start(reportPeriod, REPORT_TIME_UNIT);
         } catch (Exception e) {
             log.error("Errors during reporting to graphite, msg: {}" + e.getMessage());
         }

@@ -18,7 +18,7 @@ package org.onosproject.graphitemetrics;
 import org.onlab.metrics.MetricsReporter;
 
 /**
- * Interface of graphite reporter that reports all metrics value to graphite server.
+ * A Metric reporter interface for reporting all metrics to graphite server.
  */
 public interface GraphiteMetricsReporter extends MetricsReporter {
 }