Add owner, group, file_mode and show_diff to apache::custom_config

[treydock]

We use apache::custom_config for files that contain secrets like mod_auth_openidc so this has become necessary and would be ideal not to have to do this:

    ::apache::custom_config { 'auth_openidc':
      content        => template('openondemand/apache/auth_openidc.conf.erb'),
      priority       => false,
    }
    # Hack to set mode of auth_openidc.conf
    File <| title == 'apache_auth_openidc' |> {
      owner     => 'root',
      group     => 'apache',
      mode      => '0640',
      show_diff => false,
    }

[sheenaajay]

Thanks for submitting the PR @treydock

[sheenaajay]