Fix python scripts in src/tools/

tools/valgrind/suppressions.py

-#!/usr/bin/python
+#!/usr/bin/env python
 # Copyright (c) 2011 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 # suppressions.py
 
 """Post-process Valgrind suppression matcher.
 
 Suppressions are defined as follows:
 
@@ skipping 262 matching lines @@
   TestStack(test_stack1, positive_memcheck_suppressions,
             negative_memcheck_suppressions)
   TestStack(test_stack2, positive_heapcheck_suppressions,
             negative_heapcheck_suppressions)
   TestStack(test_stack3, positive_tsan_suppressions,
             negative_tsan_suppressions)
 
 if __name__ == '__main__':
   SelfTest()
   print 'PASS'