face: move common declarations to face-common.hpp

Change-Id: I0e3e7a93f0693b0e24ca67493a4229987e792ef4
diff --git a/tests/daemon/face/channel-fixture.hpp b/tests/daemon/face/channel-fixture.hpp
index 3e13095..2ec7d8a 100644
--- a/tests/daemon/face/channel-fixture.hpp
+++ b/tests/daemon/face/channel-fixture.hpp
@@ -27,6 +27,7 @@
 #define NFD_TESTS_DAEMON_FACE_CHANNEL_FIXTURE_HPP
 
 #include "face/channel.hpp"
+#include "face/face.hpp"
 
 #include "tests/test-common.hpp"
 #include "tests/daemon/limited-io.hpp"