fixes #6547 / BZ 1115468 - delete puppet modules from content view on repo delete

When a puppet repository is deleted (e.g. from Content -> Products),
if any of the puppet modules in that repository are associated with
an existing content view (via ContentViewPuppetModule), they need
to be removed from the content view.  This commit will do just
that, providing a behavior that is consistent with when a user
deletes a yum repository (i.e those repositories are removed
from the content view).
So i think when calculating whether or not the module is only in this repo or not, you only want to take into account Library repos.  Otherwise if i create a content view and publish, it would not be removed either as its in a 'repo'.