Fixes T12087. When transitioning into a clustered configuration for the first time, the documentation recommends using a one-device cluster as a transitional step.
However, installs may not do this for whatever reason, and we aren't as clear as we could be in warning about clusterizing directly into a multi-device cluster.
Roughly, when you do this, we end up believing that working copies exist on several different devices, but have no information about which copy or copies are up to date. Usually they all were already synchronized and are all up to date, but we can't make this assumption safely without risking data.
Instead, we err on the side of caution, and require a human to tell us which copy we should consider to be up-to-date, using bin/repository thaw --promote.