Issue 49122 - Filtered nsrole that uses nsrole crashes the
server
Bug Description: When evaluating a filter role that uses "nsrole" in the filter
crashes the server due infinite loop that leads to a stack
overflow.
Fix Description: Virtual attributes are not allowed to be used in role filters.
We were already checking for COS attributes, but not nsrole.
Also did some minor code cleanup
https://pagure.io/389-ds-base/issue/49122
Reviewed by: nhosoi(Thanks!)