Convert sbox_unittests to run exclusively on Swarming

sandbox/sbox_unittests.isolate

 # Copyright 2015 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.
 
 # Because of a limitation in isolate_driver.py, this file needs to be in
 # the same directory as the main .gyp file.
 
 {
   'conditions': [
     ['OS=="win"', {
       'variables': {
         'command': [
-          '<(PRODUCT_DIR)/sbox_integration_tests.exe',
+          '<(PRODUCT_DIR)/sbox_unittests.exe',
         ],
         'files': [
-          '<(PRODUCT_DIR)/sbox_integration_tests.exe',
+          '<(PRODUCT_DIR)/sbox_unittests.exe',
         ],
       },
     }],
     ['OS=="win" and target_arch=="ia32"', {
       'variables': {
         'files': [
           '<(PRODUCT_DIR)/wow_helper.exe',
         ],
       },
     }],
   ],
   'includes': [
     '../base/base.isolate',
   ],
 }