Fixes ticket 17903 - user needs to be active to have permissions and group permissions

To be merged on top of [pull request #2127](https://github.com/django/django/pull/2127), 06af557 and 2adb701 are the two commits of this request.

I also removed some `.save()` calls in some tests since they were not needed. This is the focus of c0a1070.
my preferred style is: "#17903 -- Inactive users shouldn't have permissions..."