LDAP and Local Authentication

I have LDAP authentication working on Grafana 6.0.1.

I have “allow_sign_up” set to false because I want to create users in Grafana manually using AD for authentication only.

When I add users in Grafana, the interface requires me to enter a password. When I try to log in, it will successfully authenticate with the correct AD password AND the local password.

Is there anything that can be done to disable local authentication for AD users?