Updating FlowObjectiveService javadoc

Change-Id: I68ab552f80bad965133aed8f90d01065d22cb974
diff --git a/core/api/src/main/java/org/onosproject/net/flowobjective/FlowObjectiveService.java b/core/api/src/main/java/org/onosproject/net/flowobjective/FlowObjectiveService.java
index 4935990..415264e 100644
--- a/core/api/src/main/java/org/onosproject/net/flowobjective/FlowObjectiveService.java
+++ b/core/api/src/main/java/org/onosproject/net/flowobjective/FlowObjectiveService.java
@@ -57,7 +57,9 @@
     int allocateNextId();
 
     /**
-     * Installs the filtering rules onto the specified device.
+     * Provides a composition policy expression.
+     * <p>
+     * WARNING: This method is a no-op in the default implementation.
      *
      * @param policy policy expression
      */