Fixes #844 #5725 - correct hosts count in puppetclass

@domcleal - Seems like using unscoped.search_for still won't get te expected results if there are any taxonomies in effect because of [how `search_by_puppetclass` works](https://github.com/theforeman/foreman/blob/develop/app/models/concerns/hostext/search.rb#L100). 
Looks like I will need to took deeper into this issue.