The Java Driver upgrade changed the behvaior of executeAsync

Now rather than blocking when the pool queue is full, it returns a future with an error. The SCC previously relied on the blocking behavior to stop issuing queries which results in usages of
joinWithCassandraTable and
saveToCassandra

Now breaking on unthrottled connections.

A workaround at the moment is to increase the number of max connections and throttle those operations. We should figure out how to get the old behavior back or adjust the throttling automatically.