config内参数合并异常
## What happens?
项目最终生成的config文件，test环境参数合并正常，其他自定义环境下，config参数合并异常。

## Mini Showcase Repository(REQUIRED)
`config.default.js`文件配置
```javascript
...
config.swaggerdoc = {
    dirScanner: './app/controller',
    apiInfo: {
      title: 'swagger',
      description: 'api swagger文档',
      version: '1.0.0',
    },
    schemes: ['http', 'https'],
    consumes: ['application/x-www-form-urlencoded'],
    produces: ['application/json'],
    securityDefinitions: {
      Bearer: {
        type: 'apiKey',
        name: 'Authorization',
        in: 'header',
      },
    },
    enableSecurity: true,
    // enableValidate: true,
    routerMap: false,
    enable: true,
  };
...
```
`config.test.js`文件配置
```javascript
...
 config.swaggerdoc = {
    enable: false,
  };
...
```
在`run/application_config_meta.json`内合并是正确的，如下：
``` 
...
 "swaggerdoc": {
    "dirScanner": "/opt/pike/api/config/config.default.js",
    "apiInfo": {
      "title": "/opt/pike/api/config/config.default.js",
      "description": "/opt/pike/api/config/config.default.js",
      "version": "/opt/pike/api/config/config.default.js"
    },
    "schemes": "/opt/pike/api/config/config.default.js",
    "consumes": "/opt/pike/api/config/config.default.js",
    "produces": "/opt/pike/api/config/config.default.js",
    "securityDefinitions": {
      "Bearer": {
        "type": "/opt/pike/api/config/config.default.js",
        "name": "/opt/pike/api/config/config.default.js",
        "in": "/opt/pike/api/config/config.default.js"
      }
    },
    "enableSecurity": "/opt/pike/api/config/config.default.js",
    "routerMap": "/opt/pike/api/config/config.default.js",
    "enable": "/opt/pike/api/config/config.test.js",
    "basePath": "/opt/pike/api/node_modules/egg-swagger-doc/config/config.default.js"
  },
...
```
但是如果用另一个自定义的配置，例如`config.lego.js`,配置和`config.test.js`保持一致，如下：
```javascript
...
 config.swaggerdoc = {
    enable: false,
  };
...
```
但是`run/application_config_meta.json`内合并之后的结果不符合预期，如下：
```javascript
...
 "swaggerdoc": {
    "dirScanner": "/opt/pike/api/config/config.default.js",
    "apiInfo": {
      "title": "/opt/pike/api/config/config.default.js",
      "description": "/opt/pike/api/config/config.default.js",
      "version": "/opt/pike/api/config/config.default.js"
    },
    "schemes": "/opt/pike/api/config/config.default.js",
    "consumes": "/opt/pike/api/config/config.default.js",
    "produces": "/opt/pike/api/config/config.default.js",
    "securityDefinitions": {
      "Bearer": {
        "type": "/opt/pike/api/config/config.default.js",
        "name": "/opt/pike/api/config/config.default.js",
        "in": "/opt/pike/api/config/config.default.js"
      }
    },
    "enableSecurity": "/opt/pike/api/config/config.default.js",
    "routerMap": "/opt/pike/api/config/config.default.js",
    "enable": "/opt/pike/api/config/config.default.js",
    "basePath": "/opt/pike/api/node_modules/egg-swagger-doc/config/config.default.js"
  },
...
```
跑`test`和`lego`环境时的脚本为：
```javascript
"start:test": "egg-scripts start --env=test --port=7260 --daemon",
"start:lego": "egg-scripts start --env=lego --port=7260 --daemon",
```
期望的话应该是合成之后的`"enable": "/opt/pike/api/config/config.lego.js"`
不过奇怪的是，`redis`的配置，在`lego`环境里面，生成的配置项是符合预期的，有来自`config.lego.js`和`config.default.js`，例如：
```
...
 "redis": {
    "client": {
      "port": "/opt/pike/api/config/config.lego.js",
      "host": "/opt/pike/api/config/config.lego.js",
      "password": "/opt/pike/api/config/config.default.js",
      "db": "/opt/pike/api/config/config.lego.js"
    },
    "default": "/opt/pike/api/node_modules/egg-redis/config/config.default.js",
    "app": "/opt/pike/api/node_modules/egg-redis/config/config.default.js",
    "agent": "/opt/pike/api/node_modules/egg-redis/config/config.default.js",
    "supportTimeCommand": "/opt/pike/api/node_modules/egg-redis/config/config.default.js"
  }
...
```