Make 3.2 client metadata log messages match 3.4+ format

It will help with processing if the messages output by 3.2 when client metadata is received in the isMaster command (added in SERVER-35854) exactly match those output by 3.4+ versions.

There is still no full support for client metadata in MongoDB 3.2, merely these log messages when the info is received, as a way of ensuring that 3.4+ compatible drivers are in use prior to upgrading the server from 3.2 to 3.4.