二级域名重定向，设置了 www 重定向到没有 www 的，怎么连其他的二级域名也被重定向了？

OS Ubuntu 14.04 LTS
nginx版本1.6.0，配置文件在最底下
因为是在本地调试(windows 8.1 update)，所以在hosts文件里添加了
192.168.1.10 mydomain.com
192.168.1.10 www.mydomain.com
192.168.1.10 test.mydomain.com

访问 http://mydomain.com/index.php正常
访问 http://www.mydomain.com/index.php正常重定向到http://mydomain.com/index.php
访问 http://test.mydomain.com/index.php也被重定向到http://mydomain.com/index.php
在IE11,watefox 26,Chrome 34上测试都这样
哪里配置错了吗？？
====================================
user nginx nginx;
master_process off;
events {
worker_connections 1024;
}
http {
gzip on;
sendfile on;
include mime.types;
default_type application/octet-stream;
keepalive_timeout 65;
server {
listen 80;
server_name www.mydomain.com;
return 301 http://mydomain.com$request_uri
}
server {
root /var/www;
listen 80;
server_name mydomain.com;
location ~* \.php$ {
include fastcgi_params;
fastcgi_pass unix:/var/run/php-fpm.sock;
fastcgi_index index.php;
fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
fastcgi_param SCRIPT_NAME $fastcgi_script_name;
}
location / {
index index.html index.htm index.php;
}
}
}
====================================