This bit got missing when we merged the new epoll acceptor for 2.0.

Disable SO_LINGER when we time out a connection due to sess_timeout,
so that we do not RST connections that have still not transmitted
their data.

git-svn-id: http://www.varnish-cache.org/svn/branches/2.0@4341 d4fa192b-c00b-0410-8231-f00ffab90ce4