Since config shard mode has both config server and shard server cluster role, reshardingopobserver will get registered twice:

1. https://github.com/10gen/mongo/blob/245928f98349a85fe51a52a7d4d22d5fa9fa9956/src/mongo/db/mongod_main.cpp#L1320
2. https://github.com/10gen/mongo/blob/245928f98349a85fe51a52a7d4d22d5fa9fa9956/src/mongo/db/mongod_main.cpp#L1344