VOM: interface's handle() retreives from singular instance

Change-Id: I262f2113f5805c0f89b615a0383efa8520184dd1
Signed-off-by: Neale Ranns <neale.ranns@cisco.com>
diff --git a/src/vpp-api/vom/interface.hpp b/src/vpp-api/vom/interface.hpp
index f11e359..181e76d 100644
--- a/src/vpp-api/vom/interface.hpp
+++ b/src/vpp-api/vom/interface.hpp
@@ -518,6 +518,11 @@
   void update(const interface& obj);
 
   /*
+   * return the interface's handle in the singular instance
+   */
+  const handle_t& handle_i() const;
+
+  /*
    * It's the OM class that calls singular()
    */
   friend class OM;