When running with config shard enabled, this test starts a sharded cluster by manually starting a mongos and connecting it to the configsvr replset (here). When running in a mixed version suite, to allow the mongos to connect to the configsvr, the test needs to run a setFCV command against the configsvr to downgrade the FCV to 7.0, just like what ShardingTest does.

This test should be disabled from sharding_last_lts_mongos_and_mixed_shards the config shard variant, since it involves running a transitionFromDedicatedConfigServer command which doesn't exist prior to 7.0.