Fix keyguardGoingAway state in KeyguardUpdateMonitor

The state is being reset too early resulting in cases where keyguard
is still dismissing but tries to start authenticate

Fixes: 37967985

Test: Open fingerprint settings, go to bouncer, unlock with pattern
      Repeat a few times, fingerprint settings is always responsive

Change-Id: I9ce59a115410c54224a57bfb14a83793d230e4f9