build: disable `-Wnon-virtual-dtor` compiler warning

See also named-data/NFD@0a05f7aea6e56a32139a6271de1f98536153a86a

Change-Id: Id615459e8b9db20ae54851b3b4808b4c5e94d3b0
diff --git a/tests/unit/tcp-bulk-insert-handle.cpp b/tests/unit/tcp-bulk-insert-handle.cpp
index 2c6a32e..9c0398b 100644
--- a/tests/unit/tcp-bulk-insert-handle.cpp
+++ b/tests/unit/tcp-bulk-insert-handle.cpp
@@ -31,9 +31,6 @@
 class TcpClient
 {
 public:
-  virtual
-  ~TcpClient() = default;
-
   void
   start(const std::string& host, const std::string& port)
   {
@@ -59,7 +56,6 @@
   {
     if (error) {
       BOOST_FAIL("TCP connection aborted");
-      return;
     }
   }
 
@@ -81,8 +77,8 @@
     guardEvent = scheduler.schedule(2_s, std::bind(&TcpBulkInsertFixture::fail, this, "Test timed out"));
   }
 
-  virtual void
-  onSuccessfullConnect(const boost::system::error_code& error)
+  void
+  onSuccessfullConnect(const boost::system::error_code& error) override
   {
     TcpClient::onSuccessfullConnect(error);