Update pre-install generated configuration for apache 2.4
https://github.com/usgs/earthquake-rtgm-calculator/blob/master/src/lib/pre-install#L73
Should support both apache 2.2 and 2.4. See hazdev-template for example: https://github.com/usgs/hazdev-template/blob/master/src/lib/pre-install.php#L60-L77