Fixes #5723 - Show hostgroups inherited via config groups in puppetclass

@eLobato 5723 specifically mentions that hostgroups are missing when added via config group. Not changing this would mean not fixing the original bug - which is possible. 
I agree that adding all hostgroups' descendants may cause this to display too much data in some cases. 
I think adding another column for config groups may cause too much clutter.
Parhaps a better solution would be to change the hostgroups column to a counter (similar to hostss) rather then list all, and have the count link to the relevant search, while making sure that the search displays all the hostgroups correctly (including those that inherit the class from parents/config groups)?