core: ignore non-Ethernet AF_LINK addresses when enumerating NICs.

Also modernize the code with some C++11 features.

Change-Id: Ibd29b39c37fdce8f87f917ab0cf48750e631e76c
diff --git a/daemon/face/ethernet-face.hpp b/daemon/face/ethernet-face.hpp
index 8f44eab..4383246 100644
--- a/daemon/face/ethernet-face.hpp
+++ b/daemon/face/ethernet-face.hpp
@@ -56,7 +56,7 @@
   };
 
   EthernetFace(const shared_ptr<boost::asio::posix::stream_descriptor>& socket,
-               const shared_ptr<NetworkInterfaceInfo>& interface,
+               const NetworkInterfaceInfo& interface,
                const ethernet::Address& address);
 
   virtual