Description of problem: There is no way to blacklist specific users from being synced if they are part of a group that is synced. Version-Release number of selected component (if applicable): OpenShift Origin 1.1
In addition to adding support for blacklisting LDAP users, we are choosing to lower the severity of out-of-scope errors, logging them instead of failing immediately on them. That PR is here: https://github.com/openshift/origin/pull/6834
User blacklists do not make sense as we require that LDAP is the system recording group membership. The specific issues that were being solved by using a user blacklist were solved by tolerating sync errors instead.