[ermine] Fix broken auth overlay

The animation was not triggering, which was keeping the overlay hidden.

Test: Login flow and lanched story in ermine
DNO-478 #done

Change-Id: I3a953b42ebb80d66bff31e7a55d5fcd527c51562
diff --git a/bin/userpicker_base_shell/lib/authentication_overlay_model.dart b/bin/userpicker_base_shell/lib/authentication_overlay_model.dart
index 8ad3329..ac146ae 100644
--- a/bin/userpicker_base_shell/lib/authentication_overlay_model.dart
+++ b/bin/userpicker_base_shell/lib/authentication_overlay_model.dart
@@ -5,7 +5,6 @@
 import 'package:fidl_fuchsia_ui_views/fidl_async.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter/scheduler.dart';
-import 'package:fuchsia_logger/logger.dart';
 import 'package:fuchsia_scenic_flutter/child_view_connection.dart'
     show ChildViewConnection;
 import 'package:lib.widgets/model.dart';
@@ -42,33 +41,19 @@
     _childViewConnection = ChildViewConnection(
       overlayViewHolderToken,
       onAvailable: (ChildViewConnection connection) {
-        log.fine(
-          'AuthenticationOverlayModel: Child view connection available!',
-        );
-        _transitionAnimation.forward();
         connection.requestFocus();
       },
       onUnavailable: (ChildViewConnection connection) {
-        log.fine(
-          'AuthenticationOverlayModel: Child view connection unavailable!',
-        );
         _transitionAnimation.reverse();
-        // TODO(apwilson): Should not need to remove the child view
-        // connection but it causes a scenic deadlock in the compositor if you
-        // don't.
-        _childViewConnection = null;
       },
     );
+    _transitionAnimation.forward();
     notifyListeners();
   }
 
   /// Stops showing a previously started overlay.
   void onStopOverlay() {
     _transitionAnimation.reverse();
-    // TODO(apwilson): Should not need to remove the child view
-    // connection but it causes a scenic deadlock in the compositor if you
-    // don't.
-    _childViewConnection = null;
     notifyListeners();
   }