Small modification regarding suppression

Now, Interest can be suppressed in both onInterest and onNack.  If there
are still good outgoing faces except incoming, onInterest will suppress.
If after invalidating the incoming face, there are still good faces
left, onNack will suppress.
diff --git a/model/ccnx-pit-entry.cc b/model/ccnx-pit-entry.cc
index 2886ed6..348f01b 100644
--- a/model/ccnx-pit-entry.cc
+++ b/model/ccnx-pit-entry.cc
@@ -107,5 +107,16 @@
   return inVain;
 }
 
+bool
+CcnxPitEntry::AreTherePromisingOutgoingFacesExcept (Ptr<CcnxFace> face) const
+{
+  bool inVain = true;
+  std::for_each (m_outgoing.begin (), m_outgoing.end (),
+                 ll::var(inVain) &=
+                 ((&ll::_1)->*&CcnxPitEntryOutgoingFace::m_face == face ||
+                  (&ll::_1)->*&CcnxPitEntryOutgoingFace::m_waitingInVain));
+
+  return !inVain;
+}
 
 }