Any chance that this fix prevents builds from finishing, if e.g. azure slave clean task thread is running? This thread might take pretty long sometimes.
I just updated from 1.606 to 1.612 and found this issue. All builds freeze in the end before triggering a downstream job. The funny part is that the builds don't even show to be running anymore in the project view, but when you open console output, you'll find the build hanging. But, when checking from Jenkins main page, you can see them still running. When the clean task thread finishes, the builds finish too.