Fixed the null-provider packet rate default value and ability to dynamically adjust the value.

Change-Id: Ifc86ff9a184f2b453038667ed32c944841ed7af6
diff --git a/providers/null/src/main/java/org/onosproject/provider/nil/NullProviders.java b/providers/null/src/main/java/org/onosproject/provider/nil/NullProviders.java
index 469feb4..f6236c4 100644
--- a/providers/null/src/main/java/org/onosproject/provider/nil/NullProviders.java
+++ b/providers/null/src/main/java/org/onosproject/provider/nil/NullProviders.java
@@ -152,7 +152,7 @@
             label = "Number of host to generate per device")
     private int hostCount = DEFAULT_HOST_COUNT;
 
-    private static final int DEFAULT_PACKET_RATE = 5;
+    private static final int DEFAULT_PACKET_RATE = 0;
     @Property(name = "packetRate", intValue = DEFAULT_PACKET_RATE,
             label = "Packet-in/s rate; 0 for no packets")
     private int packetRate = DEFAULT_PACKET_RATE;