BUG/MINOR: proto_htx: Fix htx_res_set_status to also set the reason

Becaue the check on the return value of the function http_replace_res_status was
done upside down, no reason was never set.
diff --git a/src/proto_htx.c b/src/proto_htx.c
index 6c637cb..b4bc397 100644
--- a/src/proto_htx.c
+++ b/src/proto_htx.c
@@ -2727,7 +2727,7 @@
 	if (reason == NULL)
 		reason = http_get_reason(status);
 
-	if (!http_replace_res_status(htx, ist2(trash.area, trash.data)))
+	if (http_replace_res_status(htx, ist2(trash.area, trash.data)))
 		http_replace_res_reason(htx, ist2(reason, strlen(reason)));
 }