Comment 8 for bug 1204221

Reviewed: https://review.openstack.org/38963
Committed: http://github.com/openstack/keystone/commit/5e7a56728c5c4e98dc509fb044886d6f8dd08e17
Submitter: Jenkins
Branch: master

commit 5e7a56728c5c4e98dc509fb044886d6f8dd08e17
Author: Wu Wenxiang <wu.wenxiang@99cloud.net>
Date: Sun Jul 28 22:19:42 2013 +0800

    Add defense in ldap:get_roles_for_user_and_project

    LDAP:get_roles_for_user_and_project will raise "Could not find user"
    exception when you try to get roles by user(user was in a group) and
    project.

    In this patch:
    1. Add defense in assignment.backends.ldap.Assignment::_get_metadata(),
    return empty dict rather than throw exception when userid==None or
    tenantid==None.
    2. Remove checking existance of tenant_id and user_id
    logic, because these logics were always done before this method being
    called.
    3. Add testcase test_get_role_by_user_and_project_with_user_in_group
    in test_backend module.

    Fixes bug #1204221

    Change-Id: I68c39afddde4065fc61ffb9451592c5108dc138b