Problem Description
Cron report indicates: Not using downloaded <repo_xml_file> because it is older than what we have
Problem Resolution
Simply running yum clean all should fix this, however if it returns repeatedly, you can silence the warnings for the yum cron. The start of the message will indicate which yum cron this is in reference to like this:
/etc/cron.hourly/0yum-hourly.cron
And so we know it's yum hourly. Edit /etc/yum/yum-cron-hourly.conf (or daily, or whatever the report is for). Check the debuglevel value and you'll likely find it's set to -2 which includes warnings. Change it to -3 and save the file to ensure only critical + errors are reported and you should be all set.