fix doc

doc/RUN_IN_DOCKER.md

 # How to run PaddleServing in Docker
 
+([简体中文](./RUN_IN_DOCKER_CN.md)|English)
+
 ## Requirements
 
 Docker (GPU version requires nvidia-docker to be installed on the GPU machine)
@@ -135,7 +137,7 @@ pip install paddle-serving-server-gpu
 
 ### Test example
 
-When running the GPU Server, you need to set the GPUs used by the prediction service. By default, the GPU with index 0 is used. You can configure it in two ways:
+When running the GPU Server, you need to set the GPUs used by the prediction service. By default, CPU version is used. You can configure it in two ways:
 
 1. Using the `CUDA_VISIBLE_DEVICES` environment variable, the following example specifies two GPUs with an index of 0 and 1:
 

doc/RUN_IN_DOCKER_CN.md

 # 如何在Docker中运行PaddleServing
 
+(简体中文|[English](./RUN_IN_DOCKER.md))
+
 ## 环境要求
 
 Docker（GPU版本需要在GPU机器上安装nvidia-docker）
@@ -127,7 +129,7 @@ pip install paddle-serving-server-gpu
 
 ### 测试example
 
-在运行GPU版Server时需要设置预测服务使用的GPU，缺省状态默认使用索引为0的GPU。可以通过下面两种方式进行配置：
+在运行GPU版Server时需要设置预测服务使用的GPU，缺省状态默认使用CPU。可以通过下面两种方式进行配置：
 
 1. 使用`CUDA_VISIBLE_DEVICES`环境变量，下面的示例为指定索引为0和1两块GPU：