_getSingleCategoryAcquiredMembershipList. This fixes two issues:

1. checked_permission was not propagated to recursive calls, so
   there were cases that checked_permission was ignored.
2. this method might try to get membership by acquisitions falsely,
   because _getSingleCategoryMembershipList filtered the result
   by checked_permission, so when the user was prevented from accessing
   a category directly specified by the context, the result was empty.

So the solution is to filter the result only right before returning
from this method, and stop having other methods to filter the result.


git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@30249 20353a03-c40f-0410-a6d1-a30d3c3de9de