Networking: Fix race condition that can cause missing loss-of-connection...

Networking:  Fix race condition that can cause missing loss-of-connection events.  From Max Holtzberg

ChangeLog

@@ -5502,4 +5502,7 @@
 	  changes made to pl2303, but untested (2013-9-5).
 	* arch/arm/src/sama5/sam_udphs.c:  The high-speed device side driver
 	  is now functional (although more testing is always needed) (2013-9-5).
+	* net/net_monitor.c: Fixes a race condition where a loss of connection
+	  may not be detected when the connection is lost before it has been
+	  accepted (from Max Holtzberg) (2013-9-6).
 

net/net_monitor.c

@@ -132,6 +132,17 @@ int net_startmonitor(FAR struct socket *psock)
 
   conn->connection_private = (void*)psock;
   conn->connection_event   = connection_event;
+
+  /* Check if the connection has already been closed before any callbacks have
+   * been registered. (Maybe the connection is lost before accept has registered
+   * the monitoring callback.)
+   */
+
+  if (conn->tcpstateflags == UIP_CLOSED)
+    {
+      connection_event(conn, UIP_CLOSE);
+    }
+
   return OK;
 }