Memory logging creates a non-daemon thread

The scheduling library at-at creates a thread pool with non-daemon threads. More info: https://stackoverflow.com/questions/41723408/application-not-exiting-when-using-at-at-library-in-clojure

This could be the culprit in the Percolator preventing the process for exiting on error. Fix is just to use a vanilla Thread, as this is a simple task and doesn't require a pool anyway.