Since Mockito cannot mock `final` methods, neither fields we get an `NPE` for the `final directReplyToContainers` in the `final RabbitTemplate.stop()`
* Change `mock()` to the `spy()` letting the real calls for the `final` methods.
* Fix `InboundEndpointTests` populating `Jackson2JsonMessageConverter` to the `RabbitTemplate`, because previously the stub method hasn't been called at all on the `mock` and we haven't known that there is no proper config for verification
d973295631