The discussion you've referenced is very old. And just how high is your 1.9 version? 1.9.what? Since your goal is to reach 2.5, the first step to the 'moodle march' is to upgrade your current 1.9 to the highest 1.9 available.
I assume you've done what was suggested and checked ownership/permissions on the moodledata folder as well as subfolders and files contained therein.
Since it's CentOS, one should have ssh (terminal) access as root user - unless remotely hosted on a shared server (which you've not said).
cd /var/www/
This is probably the location of the moodledata folder
Do 'ls' to see if moodledata is there.
If it is, then, chown apache:apache moodledata -R (the -R does recursive).
While you are in /var/www/ here's a suggestion I did not see:
cd /var/www/moodledata/sessions/
rm -fR *
That removes the contents (the files) in moodledata/sessions/
clear your browser cache
attempt login. If it fails, view your apache error log (on CentOS normally in /var/log/httpd/ and is called error_log for clues.
'spirit of sharing', Ken