In order to remove the --configdb parameter for MongoD, the testing infrastructure should not rely on this CLI parameter.

That is, when we add shards to the sharded cluster, we should not use the router port of the embedded router shard that is not yet added to the cluster. We can do it today because we pass the connection config server string as a CLI parameter, but not in a near future.

As the config server embedded router already knows the connection string, it is ready so serve addShard operations.

The goal of this ticket is to make the embedded router know the config server connection string from the addShard command and update the testing infrastructure to rely on the config server's router port to add new shards to the cluster. This is the first step of removing the --configdb parameter for MongoD.