Fixes #5488: Limit runlogs size

Ticket: http://www.rudder-project.org/redmine/issues/5488

To be merged in 2.11
We should not truncate that files, it seems to be read elsewhere (if the description in: https://docs.cfengine.com/docs/3.6/guide-introduction-directory-structure.html#log-files-in-var-cfengine is accurate)