bug#62163: Suppress logging shepherd evaluation in mcron.log

[Bruno Victal]

Upon mcron job completion, /var/log/mcron.log is spammed with:
“shepherd: Evaluating user expression (and (defined? (quote transient?)) (map 
(# ?) ?))”

These shepherd lines should be suppressible.


/var/log/mcron.log snippet:

--8<---------------cut here---------------start------------->8---
2023-03-13 16:52:00 243 my-heartbeat-job job: running...
2023-03-13 16:52:00 243 my-heartbeat-job job: Healthcheck: OK
2023-03-13 16:52:00 243 my-heartbeat-job job: shepherd: Evaluating user 
expression (and (defined? (quote transient?)) (map (# ?) ?)).
2023-03-13 16:52:00 243 my-heartbeat-job job: completed in 0.087s
--8<---------------cut here---------------end--------------->8---