face: Fixing small bug: after unregistering prefix, close transport if
there are no outstanding interests and prefix table is empty

Change-Id: Ie1a121fb34dfdeb10258e1ac46a8be1c9b7cdca9
diff --git a/src/face.hpp b/src/face.hpp
index e312016..42f4fd1 100644
--- a/src/face.hpp
+++ b/src/face.hpp
@@ -209,6 +209,9 @@
 
   void
   asyncUnsetInterestFilter(const RegisteredPrefixId *registeredPrefixId);
+
+  void
+  finalizeUnsertInterestFilter(RegisteredPrefixTable::iterator item);
   
   void 
   onReceiveElement(const Block &wire);