Added @Beta annotation to the flow objective API.

Change-Id: I4dd91921db1ff533b0ea1e3244dcdbf08b64a499
diff --git a/core/api/src/main/java/org/onosproject/net/flowobjective/package-info.java b/core/api/src/main/java/org/onosproject/net/flowobjective/package-info.java
index 65454a7..105f7b5 100644
--- a/core/api/src/main/java/org/onosproject/net/flowobjective/package-info.java
+++ b/core/api/src/main/java/org/onosproject/net/flowobjective/package-info.java
@@ -16,6 +16,7 @@
 
 /**
  * Abstractions for objective-based flow programming of data plane without
- * requiring device pipeline structure awareness.
+ * requiring device pipeline structure awareness.  This subsystem is
+ * experimental and its interfaces will change in the upcoming release.
  */
 package org.onosproject.net.flowobjective;
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