Mapping custom domain to the openshift wordpress blog
You need to go into your WordPress admin and change the url on the settings or options page to use your custom domain instead of the app-domain.rhcloud.com one. If you want to change it directly in the database (which i don't recommend) it is in the wp_options table under home and siteurl i believe... But I DO recommend using the WordPress admin.
Follow this article. it's step by step manual http://www.devua.co/2016/05/20/how-to-run-blog-on-openshift-complete-guide/