Add server_names_hash_bucket_size configuration

Due to the long upstream server names we use, we were getting errors on
startup. The errors mentioned that we should increase this value. Error
looks something like this ...

```
2017/10/30 19:48:54 [emerg] 1#1: could not build server_names_hash, you should increase server_names_hash_bucket_size: 64
nginx: [emerg] could not build server_names_hash, you should increase server_names_hash_bucket_size: 64
```

Sources:

* http://nginx.org/en/docs/http/ngx_http_core_module.html#server_names_hash_bucket_size
* nginx/kubernetes-ingress#34

Author: itskingori

config/http.conf

@@ -8,6 +8,7 @@ http {
   tcp_nopush            on;
   client_max_body_size  400m;
   client_body_timeout   300s;
+  server_names_hash_bucket_size 128;
 
   gzip                  on;
   gzip_comp_level       5;