Repository: flutter
Issue: iOS will show 2 LaunchScreen when localized
Labels: platform-ios,engine,a: internationalization,e: OS-version specific,has reproducible steps,P2,team-ios,triaged-ios,found in release: 3.13,found in release: 3.15

#### Summary:
I want to localize the LaunchScreen with different images, LaunchScreen will show 2 times.
First localized (Chinese) and Second Default(English).

#### Steps to Reproduce:

1. Add a new LaunchScreen-ZH.storyboard with a Logo image centered to support Chinese language.
2. add ```"UILaunchStoryboardName" = "LaunchScreen-ZH";``` to the file "ios/zh-Hans.lproj/InfoPlist.strings"
3. Set System Language to Simplified Chinese
4. Install and boot the app.

Demo project: https://github.com/shily/iOSLaunchScreenBug
#### Expected Results:
The LaunchScreen will boot with a Chinese Logo and then to MainScreen
#### Actual Results:
App boot with localized LaunchScreen-ZH.storyboard and then switch to Default LaunchScreen.storyboard before switch to Main.storyboard


#### Environments:
Devices：
> iPhone 7 with iOS 12.4
> iPhone 6s with iOS 12.4
> Simulator iPhone 6s with iOS 12.4

Flutter version: dev & stable channel both have the problem
<pre>
[✓] Flutter (Channel dev, 1.20.0-0.0.pre, on Mac OS X 10.15.5 19F101, locale en-CN)
    • Flutter version 1.20.0-0.0.pre at /Users/penguin/sdk/flutter
    • Framework revision d9653445f4 (10 days ago), 2020-06-09 18:43:03 -0400
    • Engine revision e8c13aa012
    • Dart version 2.9.0 (build 2.9.0-14.0.dev 5c1376615e)
    • Pub download mirror https://pub.flutter-io.cn
    • Flutter download mirror https://storage.flutter-io.cn

[✓] Android toolchain - develop for Android devices (Android SDK version 29.0.3)
    • Android SDK at /Users/penguin/Library/Android/sdk
    • Platform android-29, build-tools 29.0.3
    • ANDROID_HOME = /Users/penguin/Library/Android/sdk
    • Java binary at: /Applications/Android Studio.app/Contents/jre/jdk/Contents/Home/bin/java
    • Java version OpenJDK Runtime Environment (build 1.8.0_242-release-1644-b3-6222593)
    • All Android licenses accepted.

[✓] Xcode - develop for iOS and macOS (Xcode 11.5)
    • Xcode at /Applications/Xcode.app/Contents/Developer
    • Xcode 11.5, Build version 11E608c
    • CocoaPods version 1.9.3

[✓] Android Studio (version 4.0)
    • Android Studio at /Applications/Android Studio.app/Contents
    • Flutter plugin version 46.0.2
    • Dart plugin version 193.7361
    • Java version OpenJDK Runtime Environment (build 1.8.0_242-release-1644-b3-6222593)
</pre>
<pre>
[✓] Flutter (Channel stable, v1.17.4, on Mac OS X 10.15.5 19F101, locale en-CN)
    • Flutter version 1.17.4 at /Users/penguin/sdk/flutter
    • Framework revision 1ad9baa8b9 (2 days ago), 2020-06-17 14:41:16 -0700
    • Engine revision ee76268252
    • Dart version 2.8.4

[✓] Android toolchain - develop for Android devices (Android SDK version 29.0.3)
    • Android SDK at /Users/penguin/Library/Android/sdk
    • Platform android-29, build-tools 29.0.3
    • ANDROID_HOME = /Users/penguin/Library/Android/sdk
    • Java binary at: /Applications/Android Studio.app/Contents/jre/jdk/Contents/Home/bin/java
    • Java version OpenJDK Runtime Environment (build 1.8.0_242-release-1644-b3-6222593)
    • All Android licenses accepted.

[✓] Xcode - develop for iOS and macOS (Xcode 11.5)
    • Xcode at /Applications/Xcode.app/Contents/Developer
    • Xcode 11.5, Build version 11E608c
    • CocoaPods version 1.9.3

[✓] Android Studio (version 4.0)
    • Android Studio at /Applications/Android Studio.app/Contents
    • Flutter plugin version 46.0.2
    • Dart plugin version 193.7361
    • Java version OpenJDK Runtime Environment (build 1.8.0_242-release-1644-b3-6222593)
</pre>

![Screen Shot](https://user-images.githubusercontent.com/2040481/85150253-e378e680-b284-11ea-924f-d2d075b0cf05.gif)