Doesn't pass async reads to HTTP Response

[webxl]

According to https://github.com/node-red/node-red/issues/714#issuecomment-217383660, the original msg object needs to be modified and sent back for it to work. Not sure if this is the best fix (using .once() in the input event handler), but I got beanTemp.js working properly like this:

        // respond to inputs....
        this.on('input', function (msg) {
          if (this.beanConfig && this.beanConfig.device){

            this.beanConfig.device.once('temp', function(temp, valid){
              msg.topic = "temp";
              msg.payload = (temp);
              this.send(msg);
            }.bind(this));

            this.beanConfig.requestTemp();  
          } else {
            this.error('Bean not connected');
            this.send(msg);
          }
        });

        // this.beanConfig.on("connected", function() {
        //     this.beanConfig.device.on('temp', tempDataReceived);
        // }.bind(this));

At first I tried a persistent msg variable in the closure that tempDataReceived could access, but that could lead to race conditions I think. See https://node-red.slack.com/archives/general/p1476118415001635