Rudder

Similar to #3609, cf-agent tries to check that cron is running when the initial promises are run (this happens when a node just got rudder-agent installed, but has not yet been accepted by the Rudder server). On RHEL/CentOS systems, this fails as follows:

 -> Making a one-time restart promise for /usr/sbin/cron$
Proposed executable file "/etc/init.d/cron" doesn't exist
/etc/init.d/cron restart promises to be executable but isn't
I: Report relates to a promise with handle "" 
I: Made in version 'not specified' of '/var/rudder/cfengine-community/inputs/promises.cf' near line 372
I: Comment: Restarting crond

Note: this may also happen on ubuntu systems.

I will "port" the fix from #3609 to initial promises.