apps: Solving a serious bug #33 in ndn::ConsumerWindow

In certain cases, the number of in-flight packets was maintained in a
wrong way, creating inconsistencies and incorrect decision on when to
send out a new Interests.  That is, the number of in-flight
packets could be non-zero, while there were no outstanding packets at all.

Thanks to Cheng Yi for the bug discovery
diff --git a/apps/ndn-consumer-window.cc b/apps/ndn-consumer-window.cc
index 7e8325d..a2e29b3 100644
--- a/apps/ndn-consumer-window.cc
+++ b/apps/ndn-consumer-window.cc
@@ -151,8 +151,6 @@
           Simulator::Remove (m_sendEvent);
         }
 
-      // NS_LOG_DEBUG ("Window: " << m_window << ", InFlight: " << m_inFlight);
-      m_inFlight++;
       m_sendEvent = Simulator::ScheduleNow (&Consumer::SendPacket, this);
     }
 }
@@ -208,5 +206,13 @@
   Consumer::OnTimeout (sequenceNumber);
 }
 
+void
+ConsumerWindow::WillSendOutInterest (uint32_t sequenceNumber)
+{
+  m_inFlight ++;
+  Consumer::WillSendOutInterest (sequenceNumber);
+}
+
+
 } // namespace ndn
 } // namespace ns3