cache_fetch.c now reports the response code or a indicative negative
status for failed requests to the backend code.

Any timeouts, keepalives or other overhead processing of health codes
should happen in a thread in the backend handling.



git-svn-id: http://www.varnish-cache.org/svn/trunk/varnish-cache@2064 d4fa192b-c00b-0410-8231-f00ffab90ce4