AMQP-417 Fix Failing Test

- The executor thread returned its channel to the cache after the
   factory was destroyed.
- The `destroy()` method resets the connection; allowing forcing a new connection;
   it does not prevent the factory from being re-used. Adding a 'destroyed' boolean
   would change this behavior.
- Although 'dead' channels can be returned to the cache, they will be detected on
   next use, and refreshed.
- Stop the executor before destroying the CCF to fix the test case.