Make all leaf intent classes immutable

Change-Id: I45a9ac42a401b707c0c0d91f2e55294f3571ca25
diff --git a/core/api/src/main/java/org/onosproject/net/intent/PointToPointIntent.java b/core/api/src/main/java/org/onosproject/net/intent/PointToPointIntent.java
index 7dad6b8..d8434ad 100644
--- a/core/api/src/main/java/org/onosproject/net/intent/PointToPointIntent.java
+++ b/core/api/src/main/java/org/onosproject/net/intent/PointToPointIntent.java
@@ -33,7 +33,7 @@
 /**
  * Abstraction of point-to-point connectivity.
  */
-public class PointToPointIntent extends ConnectivityIntent {
+public final class PointToPointIntent extends ConnectivityIntent {
 
     private final ConnectPoint ingressPoint;
     private final ConnectPoint egressPoint;