mongos uses the ReadPreference::Nearest read preference when initializing the config version on start-up. This leaves a window open where we've set the featureCompatibilityVersion to 3.2 on a majority of our config server nodes, but mongos chooses to read from a node that hasn't applied the update the admin.system.version collection and fails sees that the featureCompatibilityVersion is 3.4.

We should update ShardingTest to await replication of the CSRS after setting the featureCompatibilityVersion of the CSRS to 3.2. This will ensure that mongos can connect to any of the nodes in the CSRS because they will all have featureCompatibilityVersion=3.2.