Instead of synchronizing on `CassandraNode.class` (which would affect all apps in the JVM, rather than just the single app), I'd prefer if we had a config key of a semaphore with one permit (e.g. see code in `JcloudsLocation.MACHINE_CREATION_SEMAPHORE`).

But looking closer, I see the synchronization is just for modifying the `QUEUED_START_NODES` so not important. Ignore this comment as you see fit!