This is the default as set in `application.yml`/`servers.yml` (https://github.com/spring-projects/spring-xd/blob/master/spring-xd-dirt/src/main/resources/application.yml#L45) - applies to all streams (by default) that don't set in the deployment properties.

However, I __do__ need to add a default for redis (currently, them ymls only have rabbit defaults).