drawer点击mask关闭时未自动重置show的状态

### Taro UI 版本信息

2.0.0-beta.2

### 问题描述

点击触发drawer并点击遮罩部分关闭后，如果再点击另一按钮触发setState，drawer会自动打开

### 复现步骤

1、点击按钮触发drawer
2、点击遮罩部分关闭drawer
3、点击页面另一按钮，该按钮触发setState
4、drawer自动打开

### 复现代码

```
// 布局部分

// 事件部分
/**
* 显示侧边栏
*/
showLeftBar() {
this.setState({
showLeftBar: true,
})
}
/**
* 侧边栏点击事件
* @param index
*/
choosePage(index) {
console.log(index)
}
/**
* 显示记账选项
*/
showRecordWay() {
this.setState({
isOpen: true,
})
}

/**
* 接收子组件传值，关闭选项遮罩
* @param openState
*/
onChangeOpenState(openState) {
this.setState({
isOpen: openState,
})
}
```

### 报错信息

drawer自动打开

### 系统信息

```
👽 Taro v1.2.12

Taro CLI 1.2.12 environment info:
System:
OS: macOS 10.14.2
Shell: 3.2.57 - /bin/bash
Binaries:
Node: 10.6.0 - /usr/local/bin/node
Yarn: 1.12.3 - /usr/local/bin/yarn
npm: 6.9.0 - /usr/local/bin/npm
npmPackages:
@tarojs/async-await: ^1.2.8 => 1.2.8
@tarojs/components: 1.2.8 => 1.2.8
@tarojs/plugin-babel: 1.2.8 => 1.2.8
@tarojs/plugin-csso: 1.2.8 => 1.2.8
@tarojs/plugin-sass: 1.2.8 => 1.2.8
@tarojs/plugin-uglifyjs: 1.2.8 => 1.2.8
@tarojs/redux: ^1.2.8 => 1.2.8
@tarojs/redux-h5: ^1.2.8 => 1.2.8
@tarojs/router: 1.2.8 => 1.2.8
@tarojs/taro: 1.2.8 => 1.2.8
@tarojs/taro-alipay: 1.2.8 => 1.2.8
@tarojs/taro-h5: 1.2.8 => 1.2.8
@tarojs/taro-swan: 1.2.8 => 1.2.8
@tarojs/taro-tt: 1.2.8 => 1.2.8
@tarojs/taro-weapp: 1.2.8 => 1.2.8
@tarojs/webpack-runner: ^1.2.8 => 1.2.8
eslint-config-taro: 1.2.8 => 1.2.8
eslint-plugin-taro: 1.2.8 => 1.2.8
nervjs: ^1.3.9 => 1.3.9
```

### 补充信息

需要手动调用onClose来在drawer关闭后修改show的状态，这点文档并没有说明