PM-2583 added (currently disabled) support for persisted metadata about sharded cluster indexes. In particular, it adds two collections, config.shard.indexes and config.csrs.indexes. Currently, this feature is not compatible with a catalog shard (ie when the config server is serving as a shard) because the methods for creating those collections will only ever make config.csrs.indexes on the config server (and when dropping the collections in setFCV downgrade), so when shard role logic runs on the config server, it will never have the config.shard.indexes collection.