Add zend opcache template to enable it

Add zend opcache template to enable it. This template is based on the opcache.ini in the php54-php-pecl-zendopcache-7.0.2-4.el6.x86_64.
I just realized, we don't need the above at all. The opcache.ini.erb won't be copied at all, when `$OPENSHIFT_PHP_OPCACHE_ENABLED=false`. See https://github.com/openshift/origin-server/blob/master/cartridges/openshift-origin-cartridge-php/usr/lib/php_config#L24