Make sure connection close does not try to stop network I/O thread in single-threaded mode
2.0+
Change log update

References #144

Conflicts:
	ChangeLog.md
Change log update
Change log update
Dispatch basic.cancel sent by RabbitMQ in the work pool

Otherwise consumers cannot re-register from handle_cancellation
because it was invoked on the network activity thread and
used a blocking method (basic.consume).

Originally reported for the Java client, this affects
Bunny because it uses a very similar internal design.