钉钉小程序按钮 hover 态样式异常

**问题描述**
钉钉小程序按钮 hover 样式态异常，长按时，背景会完全透明。

**复现步骤**
使用 tarojs/cli 2.0.0 初始化项目，引入 taro-ui，使用 AtButton，type 为 primary。
```js
加
```

**期望行为**
点击时半透明

**报错信息**
点击时全透明了

**系统信息**
```js
Taro CLI 2.0.0 environment info:
System:
OS: macOS 10.14.5
Shell: 5.3 - /usr/local/bin/zsh
Binaries:
Node: 10.17.0 - /usr/local/bin/node
Yarn: 1.10.1 - /usr/local/bin/yarn
npm: 6.11.3 - /usr/local/bin/npm
npmPackages:
@tarojs/components: 2.0.0 => 2.0.0
@tarojs/components-qa: 2.0.0 => 2.0.0
@tarojs/mini-runner: 2.0.0 => 2.0.0
@tarojs/mobx: 2.0.0 => 2.0.0
@tarojs/mobx-h5: 2.0.0 => 2.0.0
@tarojs/router: 2.0.0 => 2.0.0
@tarojs/taro: 2.0.0 => 2.0.0
@tarojs/taro-alipay: 2.0.0 => 2.0.0
@tarojs/taro-h5: 2.0.0 => 2.0.0
@tarojs/taro-qq: 2.0.0 => 2.0.0
@tarojs/taro-quickapp: 2.0.0 => 2.0.0
@tarojs/taro-swan: 2.0.0 => 2.0.0
@tarojs/taro-tt: 2.0.0 => 2.0.0
@tarojs/taro-weapp: 2.0.0 => 2.0.0
@tarojs/webpack-runner: 2.0.0 => 2.0.0
eslint-config-taro: 2.0.0 => 2.0.0
eslint-plugin-taro: 2.0.0 => 2.0.0
nerv-devtools: ^1.5.5 => 1.5.6
nervjs: ^1.5.5 => 1.5.6
stylelint-config-taro-rn: 2.0.0 => 2.0.0
stylelint-taro-rn: 2.0.0 => 2.0.0
npmGlobalPackages:
typescript: 2.5.3
```

**补充信息**