Correctly handle HTTP/1.1 EOF response

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

bin/varnishd/http1/cache_http1_proto.c

@@ -301,7 +301,7 @@ http1_body_status(const struct http *hp, struct http_conn *htc, int request)
 		return (cl == 0 ? BS_NONE : BS_LENGTH);
 	}
 
-	if (hp->protover == 11 && (request || !http_HdrIs(hp, H_Connection, "close")))
+	if (hp->protover == 11 && request)
 		return (BS_NONE);
 
 	if (http_HdrIs(hp, H_Connection, "keep-alive")) {

bin/varnishtest/tests/r01918.vtc

@@ -3,19 +3,15 @@ varnishtest "Check EOF responses work with HTTP/1.1"
 server s1 {
 	rxreq
 	txresp -nolen -bodylen 10
-	rxreq
-	txresp -hdr "Connection: close" -nolen -bodylen 10
+	close
+	accept
 } -start
 
 varnish v1 -vcl+backend {
 } -start
 
 client c1 {
-	txreq -url /1
-	rxresp
-	expect resp.status == 200
-	expect resp.bodylen == 0
-	txreq -url /2
+	txreq
 	rxresp
 	expect resp.status == 200
 	expect resp.bodylen == 10