[catapult_build] Disable everything but devil tests on Android.

catapult_build/build_steps_unittest.py

 # Copyright 2016 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.
 
 import os
 import unittest
 
 from catapult_build import build_steps
 
 
@@ skipping 19 matching lines @@
         self.assertIsInstance(test['additional_args'], list, msg=(
             'additional_args %s in build_steps._CATAPULT_TESTS %s not a list'
             % (test['additional_args'], test['name'])
         ))
       if test.get('disabled'):
         self.assertIsInstance(test['disabled'], list, msg=(
             'disabled %s in build_steps._CATAPULT_TESTS for %s not a list'
             % (test['disabled'], test['name'])
         ))
         for platform in test['disabled']:
-          self.assertIn(platform, ['win', 'mac', 'linux'], msg=(
+          self.assertIn(platform, ['win', 'mac', 'linux', 'android'], msg=(
               'Bad platform %s in build_steps._CATAPULT_TESTS for %s;'
               'should be one of "linux", "win", "mac"' % (
                   platform, test['name'])
           ))