Provide name with extension.

`a2enconf`/`a2disconf` appear to be able to make use of it, and should
help readability to know _what_ exactly is being enabled?

Author: adam-vessey

Dockerfile

@@ -80,7 +80,7 @@ LogFormat "%{X-Forwarded-For}i %h %l %u %t \"%r\" %>s %b \"%{Referer}i\" \"%{Use
 EOCONF
 
 RUN <<EOS
-a2enconf logging
+a2enconf logging.conf
 chown -R www-data /var/log/apache2
 EOS