Zimbra

Use `location` header. Trivial when #1 is done.

```
HTTP/1.1 302 Found
Cache-Control: no-store, no-cache, must-revalidate, max-age=0
Content-Language: en-US
Content-Length: 0
Content-Type: text/html;charset=UTF-8
Date: Fri, 17 Jul 2015 01:32:04 GMT
Expires: Tue, 24 Jan 2000 20:46:50 GMT
Location: https://zimbraserver/?zinitmode=http
Pragma: no-cache
X-Frame-Options: SAMEORIGIN
```
