Remove usage of custom os_package_type fact

Currently we support usage of distro packages only, and this custom
fact can be simply replaced by the default fact.

Change-Id: I6da1bfc8a392abf8808089accfed7881305d33f3

manifests/wsgi/uwsgi.pp

@@ -29,7 +29,7 @@ class gnocchi::wsgi::uwsgi (
 
   include gnocchi::deps
 
-  if $::os_package_type != 'debian'{
+  if $::operatingsystem != 'Debian'{
     warning('This class is only valid for Debian, as other operating systems are not using uwsgi by default.')
   }