Due to changes in server versions and in how certain components are built for testing, fully 25+% of specs in CI are failing on the 2.18-stable branch. These are all related to things that have been addressed in master, and with the "update build hosts" work that was done recently.

To fix this, it should be sufficient to backport https://github.com/mongodb/mongo-ruby-driver/commit/1b17ac9bbd2d6db9339093ef2a0a4b10400d8e9f to the 2.18-stable branch.