Comment 9 for bug 1211586

So, i believe the origin of this bug was a way to make horizon fall on the floor when a user navigates to the user panel, when keystone is backed by ldap. This has been addressed by the horizon team here: https://review.openstack.org/#/c/419133/

Changing behaviour based on a configuration option seems like a hack. Listing all users is fine, unless using LDAP, in which case, use filters. Let's make clients smarter and call the right APIs.