bug: autofocus input causes modal animation be incorrect on ios

# Bug Report

**Ionic version:**

[x] **4.x**

**Current behavior:**

The same issue as reported in #16136:
When setting autofocus on an ion-input element in a modal in ios, the modal content disappears.

**Expected behavior:**

The modal content does not disappear.

**Steps to reproduce:**

1. Create an Ionic App
2. Create a Modal with `const modal = await this.modalController.create({...`
3. Set autofocus on an ion-input element in the modal component

**Related code:**

`modal.component.html`:
```

Some Modal Component

Some Input

```

**Other information:**

Related issue: #16136

**Ionic info:**

```
Ionic:

ionic (Ionic CLI) : 4.12.0
Ionic Framework : @ionic/angular 4.4.0
@angular-devkit/build-angular : 0.13.8
@angular-devkit/schematics : 7.3.8
@angular/cli : 7.3.8
@ionic/angular-toolkit : 1.5.1

Cordova:

cordova (Cordova CLI) : 8.1.2 (cordova-lib@8.1.1)
Cordova Platforms : android 7.1.4, ios 4.5.5
Cordova Plugins : cordova-plugin-ionic-keyboard 2.1.3, cordova-plugin-ionic-webview 4.0.1, (and 4 other plugins)

System:

Android SDK Tools : 26.1.1
NodeJS : v11.9.0
npm : 6.9.0
OS : macOS Mojave
Xcode : Xcode 10.2.1 Build version 10E1001
```

从复现 modal.component.html 开始，并将其行为与相关 issue #16136 进行比较。在 iOS 上复现 autofocus 情况，然后在 Ionic Framework 源代码中跟踪 modal 动画以及与 ion-input 的交互。完成的标准是：autofocus 输入框处于激活状态时，modal 内容仍保持可见。

由索引模型根据 Issue 内容生成。