We failed to properly check for the end of the list of waiters.
Handle this correctly and add a test case

Fixes #428

(adopt it for 2.0 where waiter is called acceptor)



git-svn-id: http://www.varnish-cache.org/svn/branches/2.0@3966 d4fa192b-c00b-0410-8231-f00ffab90ce4