AMQPChannel::basic_cancel should have a defined or definable behavior about timing issues

[rrehbein]

Currently any basic_deliver messages received after a call to basic_cancel but before receiving basic_cancel_ok are queued, and then discarded without ack till the connection is closed.

Couple possible solutions:

• basic_cancel could reject basic_deliver messages for the cancelled consumer
• basic_cancel could continue processing basic_deliver messages for the canceled consumer till basic_cancel_ok is received. Could be done simply by adding "60,60" to the wait list in basic_cancel
• basic_cancel could have a mid-cancel callback option
• AMQPChannel could have an option for a fall-back callback option.