Fixing port stats rate calculation.

Change-Id: Ic4c803f58a53c293ae05bc0c207d7e23546f7158
diff --git a/core/api/src/main/java/org/onosproject/net/statistic/DefaultLoad.java b/core/api/src/main/java/org/onosproject/net/statistic/DefaultLoad.java
index 91af1f3..45e8537 100644
--- a/core/api/src/main/java/org/onosproject/net/statistic/DefaultLoad.java
+++ b/core/api/src/main/java/org/onosproject/net/statistic/DefaultLoad.java
@@ -28,12 +28,12 @@
     private final long current;
     private final long previous;
     private final long time;
-    private final int interval;
+    private final long interval;
 
     /**
      * Indicates the flow statistics poll interval in seconds.
      */
-    private static int pollInterval = 10;
+    private static long pollInterval = 10;
 
     /**
      * Creates an invalid load.
@@ -63,7 +63,7 @@
      * @param previous the previous value
      * @param interval poll interval for this load
      */
-    public DefaultLoad(long current, long previous, int interval) {
+    public DefaultLoad(long current, long previous, long interval) {
         checkArgument(interval > 0, "Interval must be greater than 0");
         this.current = current;
         this.previous = previous;
@@ -78,7 +78,7 @@
      *
      * @param newPollInterval poll interval duration in seconds
      */
-    public static void setPollInterval(int newPollInterval) {
+    public static void setPollInterval(long newPollInterval) {
         pollInterval = newPollInterval;
     }