openstack - use apache::site

use the newer apache::site method
rather than a file resource and have proper
symlinks again

currently, due to refactoring, we have:

@virt1000:/# if diff -q /etc/apache2/sites-enabled/wikitech.wikimedia.org
/etc/apache2/sites-available/wikitech.wikimedia.org;
then echo "confusing to have 2 different files, where one is unused"; fi

Files .. differ

Change-Id: If77393a6e6453099ccc3b1fb41bd99d27b19500c