route: Fix FIB next hop removal bug

refs: #2018

Change-Id: Id107c04d4cdce9cc756acad5d262e5c1e0cc29a8
diff --git a/src/route/nexthop-list.hpp b/src/route/nexthop-list.hpp
index 7c2011e..faf13f0 100644
--- a/src/route/nexthop-list.hpp
+++ b/src/route/nexthop-list.hpp
@@ -73,6 +73,7 @@
   }
 
   typedef std::list<NextHop>::iterator iterator;
+  typedef std::list<NextHop>::const_iterator const_iterator;
 
   iterator
   begin()
@@ -86,6 +87,18 @@
     return m_nexthopList.end();
   }
 
+  const_iterator
+  cbegin() const
+  {
+    return m_nexthopList.begin();
+  }
+
+  const_iterator
+  cend() const
+  {
+    return m_nexthopList.end();
+  }
+
   void
   writeLog();