Eliminate an unused argument.

(And Happy New Year!)
Eliminate debugging work-around, to quench a warning.
Fix NULL deref related to a backend we don't know any more.

Fixes	#1398
Make sure that we also report the obj.status in vsl
Clean up the setting of synthetic response headers a bit further,
the last fixe was clearly not enough.
Make sure we have copied all we need from the req.* http structure
for the bg-fetch, before we release the request to carry on.

Fixes	#1399