Android send_keys()无法输入

* **Macaca Version**:

* **Macaca Doctor Logs**:
macaca-doctor version: 2.0.16
Node.js checklist:

node env: /usr/local/bin/node
node version: v11.12.0

iOS checklist:

Xcode Command Line Tools is ready, version: 2354.
xcodebuild version: 10.1
iproxy[usbmuxd] is installed at: `/usr/local/bin/iproxy`
ios_webkit_debug_proxy is installed at: `/usr/local/bin/ios_webkit_debug_proxy`

Android checklist:

JAVA version is `1.8`
JAVA_HOME is set to `/Library/Java/JavaVirtualMachines/jdk1.8.0_201.jdk/Contents/Home`
ANDROID_HOME is set to `/Users/lidejuan/Library/Android/sdk`
Platforms is set to `/Users/lidejuan/Library/Android/sdk/platforms/android-28`
ADB tool is set to `/Users/lidejuan/Library/Android/sdk/platform-tools/adb`
gradle is installed, version: 5.3

Installed driver list:

android: 2.1.0
location: /usr/local/lib/node_modules/macaca-android

electron: 3.0.2
location: /usr/local/lib/node_modules/macaca-electron
* **Operate System**:
mac 10.14.3
* **Programming Language**:
Python

Log:

responseHandler.js:11:12 [master] pid:7558 Recieve HTTP Request from Client[2019-03-29 14:34:28]: method: POST url: /wd/hub/session/298e7d3b-fe1f-4360-a7db-8e89b9c8bc3e/element/13/value, jsonBody: {"value":["1","1","1","1","1","1"]}
>> proxy.js:56:14 [master] pid:7558 Proxy: /wd/hub/session/:sessionId/accept_alert:POST to http://127.0.0.1:9008/wd/hub/session/:sessionId/accept_alert:POST with body: {}
>> proxy.js:87:20 [master] pid:7558 Got response with status 200: {"sessionId":":sessionId","value":"An unknown server-side error occurred while processing the command.","status":13}
>> proxy.js:56:14 [master] pid:7558 Proxy: /wd/hub/session/298e7d3b-fe1f-4360-a7db-8e89b9c8bc3e/element/13/value:POST to http://127.0.0.1:9008/wd/hub/session/:sessionId/element/13/value:POST with body: {"value":["1","1","1","1","1","1"]}
>> proxy.js:87:20 [master] pid:7558 Got response with status 200: {"sessionId":"298e7d3b-fe1f-4360-a7db-8e89b9c8bc3e","status":0}
>> session.js:120:14 [master] pid:7558 Send HTTP Respone to Client[2019-03-29 14:34:29]: {"sessionId":"298e7d3b-fe1f-4360-a7db-8e89b9c8bc3e","status":0}

Start by reproducing the Android send_keys() failure and trace the /element/:id/value request through responseHandler.js, proxy.js, and session.js. Confirm the expected behavior for the logged request and document a passing Android input case once the command completes successfully.

Written by the indexing model from the issue text.