fix use filecache issue in query_tool, a=chris

diff --git a/bin/arc_tool.php b/bin/arc_tool.php
index 5b94928b3..590fbd995 100755
--- a/bin/arc_tool.php
+++ b/bin/arc_tool.php
@@ -49,6 +49,9 @@ if(!PROFILE) {
 /** NO_CACHE means don't try to use memcache*/
 define("NO_CACHE", true);

+/** USE_CACHE false rules out file cache as well*/
+define("USE_CACHE", false);
+
 /** Load the class that maintains our URL queue */
 require_once BASE_DIR."/lib/web_queue_bundle.php";