[ONOS-5607] Revise LISP ctrl impl class to track msgs and routers

Change-Id: I4a51a8ef9162e3feee543f40fa92a0435186d1c9
diff --git a/protocols/lisp/api/src/main/java/org/onosproject/lisp/ctl/LispController.java b/protocols/lisp/api/src/main/java/org/onosproject/lisp/ctl/LispController.java
index 5c47109..1a3641d 100644
--- a/protocols/lisp/api/src/main/java/org/onosproject/lisp/ctl/LispController.java
+++ b/protocols/lisp/api/src/main/java/org/onosproject/lisp/ctl/LispController.java
@@ -29,6 +29,13 @@
     Iterable<LispRouter> getRouters();
 
     /**
+     * Obtains all subscribed LISP routers known to this LISP controllers.
+     *
+     * @return Iterable of LISP router elements
+     */
+    Iterable<LispRouter> getSubscribedRouters();
+
+    /**
      * Obtains the actual router for the given LispRouterId.
      *
      * @param routerId the router to fetch