Run with S6 instead of chaperone

conf/chaperone.d/clean-heldmsg-cron.conf

-clean_heldmsg_cron.service: {
-    type: cron,
-    interval: "50 4 * * *",
-    command: "/usr/local/bin/clean-heldmsg",
-    env_set: {
-        "LC_ALL": "C",
-        "LC_CTYPE": "C"
-    }
-}