Buggy connections could crash node.js. Now check connection before sending data every time

http://groups.google.com/group/nodejs/browse_thread/thread/16abfa87c32408f3

We have our node.js server monitored by monit, however it seems monit is pretty
agressive / quick about closing its connection and thus we've gotten into a
loop of errors like this:

    at #<a ServerResponse>.flush
    at #<a ServerResponse>.sendBody
    at [object Object].json
    at [object Object].[anonymous]
    at [object Object].[anonymous]
    at [object Object].[anonymous]
http.js:353: Socket is not open for writing
      connection.send(out, out.encoding);
                 ^

Below is a patch that basically cause flushMessageQueue to check the connection
state for each item in the queue rather than just a single time in the
beginning.

src/http.js

@@ -341,14 +341,13 @@ function createIncomingMessageStream (connection, incoming_listener) {
 /* Returns true if the message queue is finished and the connection
  * should be closed. */
 function flushMessageQueue (connection, queue) {
-  if (connection.readyState !== "open" && connection.readyState !== "writeOnly") {
-    return false;
-  }
-
   while (queue[0]) {
     var message = queue[0];
 
     while (message.output.length > 0) {
+      if (connection.readyState !== "open" && connection.readyState !== "writeOnly") {
+        return false;
+      }
       var out = message.output.shift();
       connection.send(out, out.encoding);
     }