[MINOR] http: take a capture of truncated responses

If a server starts to respond but stops before the body, then we
capture the truncated response. We don't do this on the request
because it would happen too often upon stupid attacks.
diff --git a/src/proto_http.c b/src/proto_http.c
index 7f37002..439e1ce 100644
--- a/src/proto_http.c
+++ b/src/proto_http.c
@@ -4815,9 +4815,9 @@
 			return 0;
 		}
 
-		/* close from server */
+		/* close from server, capture the response if the server has started to respond */
 		else if (rep->flags & BF_SHUTR) {
-			if (msg->err_pos >= 0)
+			if (msg->msg_state >= HTTP_MSG_RPVER || msg->err_pos >= 0)
 				http_capture_bad_message(&s->be->invalid_rep, s, rep, msg, msg->msg_state, s->fe);
 
 			s->be->be_counters.failed_resp++;