The bouncestorage image hasn't been updated for 4 years and has this
message at the top of the docs:
This repository is outdated; please use dockerswiftaio/docker-swift instead.
However, dockerswiftaio/docker-swift hasn't been updated for 2 years.
Switch to openstackswift/saio instead, which is getting regular updates.
This requires some minor changes to one test, and how we start the
container.