Don't define FACTERLIB when applying horizon manifest

We are exporting FACTERLIB so that we can use custom facts, this is causing
problems with the apache module. We don't need custom facts for
horizon so as a workaround we don't define FACTERLIB when applying
the horizon puppet module
https://bugzilla.redhat.com/show_bug.cgi?id=902020

A fix has been submited to the apache puppet module, once we rebase
the puppet modules we're using this commit should be reverted
https://github.com/puppetlabs/puppetlabs-apache/pull/138

Change-Id: Ibe9b5229b6f10df2a6993231289565749fe180d9