SOFTWARE-1643 generator cronjob fixes

This is two commits to fix up the condor_ce_config_generator cronjob as per ticket [SOFTWARE-1643](https://jira.opensciencegrid.org/browse/SOFTWARE-1643): the first patch adds /usr/sbin to the PATH so condor_ce_reconfigure can run condor_reconfig; the second patch changes the frequency from every 10 minutes to every 6 hours.