core: slim down `common.hpp`

Change-Id: I875c35147edd2261fbaa24e809c170d5cd9b94d3
diff --git a/daemon/face/ethernet-channel.hpp b/daemon/face/ethernet-channel.hpp
index c675a52..86a3bc8 100644
--- a/daemon/face/ethernet-channel.hpp
+++ b/daemon/face/ethernet-channel.hpp
@@ -33,6 +33,8 @@
 #include <boost/asio/posix/stream_descriptor.hpp>
 #include <ndn-cxx/net/network-interface.hpp>
 
+#include <map>
+
 namespace nfd::face {
 
 /**