management: fix backwards compatibility for deprecated nfd-face-flags.hpp header

Change-Id: Ic3a3442c5975e7ad407f8f1417c10e74021337e3
refs: #1992
diff --git a/src/management/nfd-face-flags.hpp b/src/management/nfd-face-flags.hpp
new file mode 120000
index 0000000..24090c2
--- /dev/null
+++ b/src/management/nfd-face-flags.hpp
@@ -0,0 +1 @@
+nfd-face-traits.hpp
\ No newline at end of file