daemon: mark some classes and methods 'final'

As suggested by gcc's -Wsuggest-final-types and -Wsuggest-final-methods

Change-Id: I1622857ee53581efd0c6ce3fe93199c72202d817
diff --git a/daemon/face/udp-channel.hpp b/daemon/face/udp-channel.hpp
index c3f696d..25e735a 100644
--- a/daemon/face/udp-channel.hpp
+++ b/daemon/face/udp-channel.hpp
@@ -37,7 +37,7 @@
 /**
  * \brief Class implementing UDP-based channel to create faces
  */
-class UdpChannel : public Channel
+class UdpChannel final : public Channel
 {
 public:
   /**
@@ -53,13 +53,13 @@
              size_t defaultMtu);
 
   bool
-  isListening() const override
+  isListening() const final
   {
     return m_socket.is_open();
   }
 
   size_t
-  size() const override
+  size() const final
   {
     return m_channelFaces.size();
   }