Variable upstream should be locally scoped

Because `upstream` is defined in the foreach loop, there should be no `@`, because the global `@upstream` is undefined. This results in an empty upstream definition:

```
upstream pino {
   
-  server  fail_timeout=0;
+  server unix:/var/run/gunicorn/pino.sock fail_timeout=0;
   
}
```
Merge pull request #11 from ByteInternet/master

Variable upstream should be locally scoped