docker proxy

mkdir -p /etc/systemd/system/docker.service.d
vim /etc/systemd/system/docker.service.d/http-proxy.conf
加入如下内容：
```
[Service]
Environment="HTTP_PROXY=http://proxy-addr:proxy-port" "HTTPS_PROXY=http://proxy-addr:proxy-port" "NO_PROXY=localhost,127.0.0.1,docker-registry.somecorporation.co
```
重启服务：
systemctl daemon-reload
systemctl restart docker