Currently, to convert a replica set to a sharded cluster users are required to invoke addShard which executes listDatabases on the shard being added and registers existing databases in config.databases.

In the future, users will be able to call transitionToShardedCluster which does not call (yet?) into addShard. Tests calling into transitionToShardedCluster are currently explicitly invoking enabledSharding in order to work around the issue.