rather use the alias and keep references consistent

Using the variable reference also breaks rspec-puppet
tests with compile.with_all_deps as it won't be able
to fully resolve all the dependencies.

Change-Id: Ica4bd1d3336d59d66d8da01194bba825d958943a

manifests/wsgi/apache.pp

@@ -101,7 +101,7 @@ class horizon::wsgi::apache (
 # - ${priority}-${vhost_conf_name}.conf
 # - ${priority}-${vhost_ssl_conf_name}.conf
 #",
-    require => Package[$::horizon::params::package_name],
+    require => Package['horizon'],
   }