Create the cron.allow file with correct permissions

This way we will ensure that the file is created with correct
owner and permissions from the beginning.

Uses the new parameters of the file_existence template.
These options aren't checked by OVAL, they are only used by
remediations.

linux_os/guide/services/cron_and_at/restrict_at_cron_users/file_cron_allow_exists/rule.yml

@@ -41,3 +41,5 @@ template:
     vars:
         filepath: /etc/cron.allow
         exists: true
+        fileuid: "0"
+        filemode: "0600"