Update scripts to specify python2

Also remove zipfile from update.py as that path was removed
upstream.

Bug: 185400108
Test: they run
Change-Id: Iff693cf656a9bbdcf7960d8beb4626315e7af57f
diff --git a/systrace.py b/systrace.py
index 71da650..7bd4537 100755
--- a/systrace.py
+++ b/systrace.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python2
 
 # Copyright (c) 2015 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be