Fixed #8552 -- Use the LOGIN_REDIRECT_URL setting in the auth tests, rather than hard-coding the value.

This enables things to work properly when installed in other configurations.
Patch from aeby.


git-svn-id: http://code.djangoproject.com/svn/django/trunk@8613 bcc190cf-cafb-0310-a4f2-bffc1f526a37