communication: improve constness

Change-Id: Iabc5093d3c8e84540ddef4f6f2ff768dd9f3d0da
refs: #4472
diff --git a/src/communication/sync-logic-handler.hpp b/src/communication/sync-logic-handler.hpp
index 3a074ef..46bb18f 100644
--- a/src/communication/sync-logic-handler.hpp
+++ b/src/communication/sync-logic-handler.hpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /**
- * Copyright (c) 2014-2017,  The University of Memphis,
+ * Copyright (c) 2014-2018,  The University of Memphis,
  *                           Regents of the University of California,
  *                           Arizona Board of Regents.
  *
@@ -61,7 +61,7 @@
     }
   };
 
-  SyncLogicHandler(ndn::Face& face, const IsLsaNew& isLsaNew, ConfParameter& conf);
+  SyncLogicHandler(ndn::Face& face, const IsLsaNew& isLsaNew, const ConfParameter& conf);
 
   /*! \brief Hook function to call whenever sync detects new data.
    *