Fix default Apache config cleanup on Ubuntu

The configuration file /etc/apache2/conf.d/openstack-dashboard.conf
is not properly cleaned on Ubuntu platforms.

The configuration file is actually a symbolic link and
it looks like Puppet cannot manage its content if ensure
is present is used on the file resource.

This bug manifests itself with Puppet <= 3.2.x:
https://projects.puppetlabs.com/issues/6808

Updating the actual file on Ubuntu platforms fixes the problem.

Closes-bug: #1382222
Change-Id: I673d991f0de4d899cffc07a8ec6d60dbc4a1fb39
Merge "Fix default Apache config cleanup on Ubuntu"