Changed recipe_modules base paths to be abstract entities in their own right.

scripts/slave/recipe_modules/chromium_android/example.expected/gerrit_try_builder_basic.json

 [
   {
     "cmd": [
       "python",
       "-u",
       "\nimport os, sys\n\nbuild_path = sys.argv[1]\nif os.path.exists(build_path):\n  for (path, dir, files) in os.walk(build_path):\n    for cur_file in files:\n      if cur_file.endswith('index.lock'):\n        path_to_file = os.path.join(path, cur_file)\n        print 'deleting %s' % path_to_file\n        os.remove(path_to_file)\n",
       "[SLAVE_BUILD]"
     ],
     "name": "cleanup index.lock",
     "~followup_annotations": [
@@ skipping 233 matching lines @@
       "[DEPOT_TOOLS]/git_number.py"
     ],
     "cwd": "[SLAVE_BUILD]/src",
     "name": "git_number",
     "stdout": "/path/to/tmp/"
   },
   {
     "cmd": [
       "python",
       "-u",
-      "[BUILD]/scripts/slave/recipe_modules/adb/resources/list_devices.py",
+      "RECIPE_MODULE[adb]/resources/list_devices.py",
       "['[SLAVE_BUILD]/src/third_party/android_tools/sdk/platform-tools/adb', 'devices']",
       "/path/to/tmp/json"
     ],
     "name": "List adb devices",
     "~followup_annotations": [
       "@@@STEP_LOG_LINE@json.output@[@@@",
       "@@@STEP_LOG_LINE@json.output@  \"014E1F310401C009\"@@@",
       "@@@STEP_LOG_LINE@json.output@]@@@",
       "@@@STEP_LOG_END@json.output@@@"
     ]
@@ skipping 202 matching lines @@
       "[SLAVE_BUILD]/src/build/android/asan_symbolize.py",
       "-l",
       "[SLAVE_BUILD]/src/out/Release/full_log"
     ],
     "env": {
       "PATH": "[SLAVE_BUILD]/src/third_party/android_tools/sdk/platform-tools:[SLAVE_BUILD]/src/build/android:%(PATH)s"
     },
     "name": "stack_tool_for_asan"
   }
 ]