Int 3460: Support output-channel when an AbstractCorrelatingMessageHandler is 'ref'd by a Service Activator	

INT-3460: Support output-channel when an AbstractCorrelatingMessageHandler is 'ref'd by a Service Activator	

* allow AbstractCorrelatingMessageHandler's output referenced by service-activator output-channel
* add test 
No. Gary means this:
```
// should never happen but just return it if it's already an ARPMH
```
to this
```
// should never happen but just return it if it's already an AMPMH
```
See?