用例运行失败后重试导致手机重启

* **Macaca Version**:
2.0.4
* **Macaca Doctor Logs**:
macaca-doctor version: 2.0.1

Node.js checklist:

node env: /usr/local/bin/node
node version: v7.7.1

iOS checklist:

Xcode Command Line Tools is ready, version: 2347.
xcodebuild version: 8.3.2
iproxy[usbmuxd] is installed at: `/usr/local/bin/iproxy`
ios_webkit_debug_proxy is installed at: `/usr/local/bin/ios_webkit_debug_proxy`
carthage is installed, version: 0.24.0

Android checklist:

JAVA version is `1.8.0_121`
JAVA_HOME is set to `/Library/Java/JavaVirtualMachines/jdk1.8.0_121.jdk/Contents/Home`
ANDROID_HOME is set to `/Users/xiaoxue/Library/android-sdk-macosx`
Platforms is set to `/Users/xiaoxue/Library/android-sdk-macosx/platforms/android-25`
ADB tool is set to `/Users/xiaoxue/Library/android-sdk-macosx/platform-tools/adb`
gradle is installed, version: 3.5

Installed driver list:

android: 2.0.30
chrome: 1.0.6
electron: 1.1.7
ios: 2.0.22
* **Operate System**:
OSX 10.12.3
Android: 5.1.1
品牌：红米3
* **Programming Language**:
python

* **错误概况**
由于 [https://github.com/alibaba/macaca/issues/656](#656)错误，所以在没有重启macaca server的情况下，直接重新运行用例，一般重试第3次，有90%以上概率导致手机自动重启。