Varnish does not recognize req.hash
Solution 1:
Direct quote from https://www.varnish-cache.org/docs/3.0/installation/upgrade.html#req-hash-is-replaced-with-hash-data
In Varnish 3.x, req.hash is replaced with hash_data.
You no longer append to the hash with +=, so:
set req.hash += req.url;
becomes
hash_data(req.url);