tests+tools: fix build with clang-5.0

Change-Id: I75eeb01b071c1702517a65a8099e52d4092a4638
Refs: #4278
diff --git a/tools/nfd-autoreg.cpp b/tools/nfd-autoreg.cpp
index 39b7f6b..cb0bdd2 100644
--- a/tools/nfd-autoreg.cpp
+++ b/tools/nfd-autoreg.cpp
@@ -213,7 +213,7 @@
                                    faceStatus.getFacePersistency());
         }
       },
-      [this] (uint32_t code, const std::string& reason) {});
+      [] (uint32_t code, const std::string& reason) {});
   }
 
   int