Fix for 3.1.3

Prior to this commit pe-httpd would not start due to this error:

```
[root@puppetmaster01 ~]# service pe-httpd start
Starting pe-httpd: Syntax error on line 26 of
/etc/puppetlabs/httpd/conf.d/puppetmaster.conf:
Invalid command 'RackAutoDetect', perhaps misspelled or defined by a
module not included in the server configuration
                                                           [FAILED]
                                                           ```