mediawiki_singlenode: apache 2.4 compat

Add <IfVersion> guards to the mediawiki_singlenode Apache site configuration
that use the new Require directives to setup access rather than the old
Allow / Deny directives.

Change-Id: Icad1070cf781168f434437d33d6ddd13d33196f5
Merge "mediawiki_singlenode: apache 2.4 compat" into production