Fix android modal not disappear when reload (#27542)

Summary:
Fixes https://github.com/facebook/react-native/issues/17986

See above issue

After apply this change:
![ezgif-4-45d9add85b74](https://user-images.githubusercontent.com/615282/70987576-2520ad00-20fb-11ea-9b90-c9a7839824a5.gif)

## Changelog

[Android] [Fixed] - Fix android modal not disappear when reload
Pull Request resolved: https://github.com/facebook/react-native/pull/27542

Test Plan: Open a modal and do a refresh to see whether it disappears

Differential Revision: D19178803

Pulled By: mdvacca

fbshipit-source-id: 61894927fc481650804b2196df06a80c16b64e6c

ReactAndroid/src/main/java/com/facebook/react/views/modal/ReactModalHostView.java

@@ -96,6 +96,12 @@ public class ReactModalHostView extends ViewGroup implements LifecycleEventListe
     // Do nothing as we are laid out by UIManager
   }
 
+  @Override
+  protected void onDetachedFromWindow() {
+    super.onDetachedFromWindow();
+    dismiss();
+  }
+
   @Override
   public void addView(View child, int index) {
     UiThreadUtil.assertOnUiThread();