reply_q not re-created

[Flavio Percoco]

oslo.messaging doesn't re-declare the "reply_q" exchange when reconnects happen.

It's possible to see this from these 2 links[0][1]. The former shows the `on_reconnection` code and the later shows the method that returns the `reply_q` where replies should be sent. The on_reconnection function calls the `declare` method on the consumer but the `Consumer`'s `declare` method does not re-create the exchange instance[2].

[0] https://github.com/openstack/oslo.messaging/blob/master/oslo_messaging/_drivers/impl_rabbit.py#L660-L670
[1] https://github.com/openstack/oslo.messaging/blob/master/oslo_messaging/_drivers/amqpdriver.py#L287-L302
[2] https://github.com/openstack/oslo.messaging/blob/master/oslo_messaging/_drivers/impl_rabbit.py#L205-L209

A way to reproduce this bug is to have a ReplyWaiter instanciated and restart rabbitmq. Consumer's declares will be called but, in the case of non durable exchanges, the exchange won't be re-created.

[Mehdi Abaakouk (sileht)]

After investigation, this is the well known bug about certain connections that doesn't detect the disconnection.

This is fixed by enabling heartbeat or set low values to the system tcp_keepalives*.