Revert of depot_tools: add test_api to infra_paths recipe module

recipe_modules/infra_paths/example.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.
 
 DEPS = [
   'infra_paths',
-  'recipe_engine/path',
   'recipe_engine/platform',
   'recipe_engine/properties',
   'recipe_engine/step',
 ]
 
 from recipe_engine.config_types import Path
 
 def RunSteps(api):
   api.step('step', [], cwd=api.infra_paths['slave_build'])
 
-  if api.path.exists(api.infra_paths['slave_build'].join('foo.txt')):
-    api.step('path exists', [])
-
 
 def GenTests(api):
   for platform in ('linux', 'win', 'mac'):
-    yield (api.test(platform) +
-           api.platform.name(platform) +
-           api.infra_paths.exists(
-               api.infra_paths['slave_build'].join('foo.txt')))
+    yield (api.test(platform) + api.platform.name(platform))
 
     yield (api.test('%s_kitchen' % platform) +
            api.platform.name(platform) +
            api.properties(path_config='kitchen'))