On a stock CentOS 6 server, apache server is configured via /etc/httpd/conf/httpd.conf.
Without any additional control panel, by default, apache and the web service uses /var/www/. Document root is html (moodle code would go in there normally). And since apache has already been configured to use /var/www as it's 'home' directory, moodledata placed there normally has no issues ... again, that's on a stock CentOS 6 machine with no control panel.
You could either try above locations or ...
Look in httpd.conf for a section on 'user' directories. From what you've shared so far, /home/user/public_html/ is a user directory and would be restricted from using anything outside public_html.
'spirit of sharing', Ken