Unit test for 6c2c1c1, restricted for now to:

- ActiveMQ, any protocol level
- Apollo, protocol level 1.0

Redeliveries currently fail for:
- Apollo, protocol levels 1.1 and 1.2
- RabbitMQ, any protocol level

Cause: TBD
Gem version 1.2.13
Merge branch 'master' into dev
Prevent dup subscription header on re-receive.