Don't let face failures override face lockout messages

There's no guarantee what order framework sends the
face auth failure vs face auth error (lockout) callbacks,
so guard against overriding a lockout message with
a failure message.

Fixes: 337726884
Flag: EXEMPT bugfix
Test: atest BouncerMessageInteractor
Test: Fail face auth until lock out on primary bouncer. Observe
lockout message shows; not face auth failure message.

Change-Id: Icb58b4d4067ebc07060d4d37d8e4be1e59797dc6