reshardCollection command is shuffling data even when requested shard key already matches

The reshardCollection command should instead return {ok: 1} without migrating any data when the request shard key pattern already matches the current one.

The reshardCollection command is a long-running operation and the client's connection may get disconnected. It is important for the reshardCollection command to be manually retried by the client without causing a new instance of resharding the collection to occur had the earlier instance already completed.