[ovirt-users] LDAP authentication does not work after engine upgrade to ovirt 4.6

I've just upgraded our ovirt engine server to ovirt 4.6 and it appears that LDAP logins no longer work.  When I attempt to log in using an AD account the following errors are shown in the engine log. 2018-09-11 10:03:44,610-04 ERROR [org.ovirt.engine.core.sso.servlets.InteractiveAuthServlet] (default task-10) [] Internal Server Error: Cannot locate principal 'username(a)example.com' 2018-09-11 10:03:44,610-04 ERROR [org.ovirt.engine.core.sso.utils.SsoUtils] (default task-10) [] Cannot locate principal 'username(a)example.com' 2018-09-11 10:03:44,645-04 ERROR [org.ovirt.engine.core.aaa.servlet.SsoPostLoginServlet] (default task-10) [] server_error: Cannot locate principal 'username(a)example.com' I have not changed any LDAP settings and ldapsearch is able to find this object without any issues.  Does anybody have any idea what would cause this?