Commit e142a199 for Issue #1918 fixed up the case where the
server sends an HTTP/1.1 response with no Content-Length, no
Transfer-Encoding, but with Connection:close.

This fixes the very similar case where all the conditions are the
same except that there's also no Connection: close header, but the
content is still implicitly delimited by the server closing the
connection.

This behavior has been observed from multiple versions of Apache
with WSGI applications behind it, resulting in broken
Content-Length:0 responses from Varnish.

Ref: varnishcache/varnish-cache#1954