ipapermission: Fix attrs and drop privilege handling

The attrs handling was not complete and did not support to ensure presence
or absence of attributes with action:member.

The includedattrs and excludedattrs parameters have not been added with
this change as the use of attrs will automatically set includedattrs and
excludedattrs. The includedattrs and excludedattrs parameters are only
usable for managed permissions and duplicating attrs.

The permission module may not handle privileges. An IPA internal only API
has been used for this. The prvilege variable and all related code paths
have been removed.

Fixes: #424 ([Permission Handling] Not able to add additional attributes
             with existing attributes)
Fixes: #425 ([Permission Handling] Not able to add member privilege while
             adding permission)