First of all, let's install MySQL-community-server 5.7 on fresh CentOS 6.
--------------- On RHEL/CentOS 6 --------------- # wget http://dev.mysql.com/get/mysql57-community-release-el6-7.noarch.rpm
# yum localinstall mysql57-community-release-el6-7.noarch.rpm
# yum repolist enabled | grep "mysql.*-community.*"