JIRA: https://jira.spring.io/browse/INT-4226
Since `rabbitTemplate` properly implement `receive()` with `timeout` it looks organic to delegate a `PollableChannel.receive(timeout)` there.
* Refactor `PollableAmqpChannel` to properly delegate `PollableChannel.receive(timeout)` implementation
* Refactor `ChannelTests` to perform `PollableAmqpChannel.receive(timeout)` directly instead of `Thread.sleep()` loop
* Get rid of `BrokerRunning` in favor of the same rule from the `spring-rabbit-junit` dependency
Doc Polishing
Fix DSL AmqpTests
257a2d3dab