No close conn

We'd like to be able to make multiple calls via celery through the same connection.

For that to be possible we have to keep the connection open after a call to the ```PostTask``` function (see change in  amqplibconnector.php) and not to try to connect at each push (celery.php).

As we don't want to read any response from our queue server and we want to limit the number of connections we open to it I also added a parameter to the ```PostTask``` function that keep it from returning an ```AsyncResult```.