Added @Beta annotation to the flow objective API.

Change-Id: I4dd91921db1ff533b0ea1e3244dcdbf08b64a499
diff --git a/core/api/src/main/java/org/onosproject/net/flowobjective/Objective.java b/core/api/src/main/java/org/onosproject/net/flowobjective/Objective.java
index 0d53a75..090c298 100644
--- a/core/api/src/main/java/org/onosproject/net/flowobjective/Objective.java
+++ b/core/api/src/main/java/org/onosproject/net/flowobjective/Objective.java
@@ -15,6 +15,7 @@
  */
 package org.onosproject.net.flowobjective;
 
+import com.google.common.annotations.Beta;
 import org.onosproject.core.ApplicationId;
 
 import java.util.Optional;
@@ -22,6 +23,7 @@
 /**
  * Base representation of an flow description.
  */
+@Beta
 public interface Objective {
 
     static final boolean DEFAULT_PERMANENT = true;