Fixes #6352: Lowercase hostnames in certs

This is the same fix as aad7619 in puppet-foreman[1].

Relevant parts from http://projects.theforeman.org/issues/6352

facter fqdn and hostname -f both return
HOSTNAME.domain.com

Starting httpd: [Tue Jun 24 13:26:59 2014] [warn] module passenger_module is already loaded, skipping
Syntax error on line 37 of /etc/httpd/conf.d/25-puppet.conf:
SSLCertificateFile: file '/var/lib/puppet/ssl/certs/HOSTNAME.domain.com.pem' does not exist or is empty
[FAILED]

There is a .pem file generated in /var/lib/puppet/certs/, but it is in
lowercase.

[1]: https://github.com/theforeman/puppet-foreman/commit/aad76195117479ca6b2cbbf9f0579e3672a9c806