The credit_flow between publishing AMQP 0.9.1 channel (or MQTT
connection) and (non-mirrored) classic queue processes was
unintentionally removed in 4.0 together with anything else related to
CQ mirroring.
By default we restore the 3.x behaviour for non-mirored classic
queues. It is possible to disable flow-control (the earlier 4.0.x
behaviour) with the new env `classic_queue_flow_control`. In 3.x this
was possible with the config `mirroring_flow_control`.
(cherry picked from commit d65bd7d07a)
2c1f1a1387