Add max channels config

[luisfmcalado]

trafficstars

If you setup rabbitmq with the default configuration the amqp plugin won't be able to tune the connection and the load test script will fail. The default was add in https://github.com/rabbitmq/rabbitmq-server/issues/1593.

With this change we are able to configure the max channels for the connection.

<amqp type="connection.open" vhost="/" channel_max="2047"></amqp>

[tisba]

I'd say this looks good, could you maybe take another look, @nniclausse? I'm not familiar with AMQP…

[NAR]

I faced the same problem (couldn't connect to RabbitMQ), this patch and the configuration update (add the channel_max attribute) solves the problem. Highly useful change.

[luisfmcalado]

@tisba @nniclausse can this be merged?