Update on DRILL-1491 - The illegal state transition (cancellation_requested -> enqueued) is no longer happening for me after I updated my JDK to the latest version. I'll try on and off over the weekend and if it cannot be reproduced, I'll let it go.
Release plan - I'll merge the PRs for DRILL-1491 and DRILL-4547 in a bit. I'm planning on rolling out release candidate RC0 on Monday morning (PDT). I'll create a branch for the release. Apache master is still open for commits. (Try not to break anything).
