How configure Varnish Caché for Modx Manager?

I new in this topic, I installed Varnish Cache 4.0 on a CentOS Server, it works fine, I have a site that is using ModX as CMS, In my VCL file I have the function sub vcl_recv the next lines:

sub vcl_recv {

    if(req.url ~ "^/manager/"){
            return(pass);
    }else{
            unset req.http.cookie;
    }
}

If I logged in in the manager CMS I can see my documents, and edited but when try to save it the manager logout and close the session. How can I do for solve it?

Thanks a lot!