This ticket is to ensure there is adequate multiversion testing
coverage for this project.
1. Test that this feature works correctly on mixed binary version
clusters.
2. Test how the feature behaves when upgrading FCV turns the
feature on
3. Test that the correct behavior occurs when downgrading FCV
completely and then upgrading FCV completely
4. Test that the correct behavior occurs if the FCV upgrade fails.
5. Test that the correct feature behavior occurs if the FCV downgrade
fails after only reaching the `downgrading` FCV state and then FCV is
fully upgraded again
6. Test that anything added by this project to the setFCV command
must be idempotent/retryable.
7. If concurrency between this feature and the setFCV command is a
concern, test that it works correctly.

Some of these tests may not be relevant for every project; please
explicitly state if that is the case. If some of these tests will be
covered by already existing tests/passthroughs, please explicitly
state that.