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

scripts/slave/recipes/android/appurify.expected/Android_Tests__amp__dbg__basic.json

 [
   {
     "cmd": [
       "python",
       "-u",
       "[BUILD]/scripts/slave/bot_update.py",
       "--master",
       "chromium.fyi",
       "--builder",
       "Android Tests (amp)(dbg)",
@@ skipping 96 matching lines @@
       "[SLAVE_BUILD]/src/build/tree_truth.sh",
       "[SLAVE_BUILD]/src",
       "src"
     ],
     "name": "tree truth steps"
   },
   {
     "cmd": [
       "python",
       "-u",
-      "[BUILD]/scripts/slave/recipe_modules/gsutil/resources/gsutil_wrapper.py",
+      "RECIPE_MODULE[gsutil]/resources/gsutil_wrapper.py",
       "--",
       "[DEPOT_TOOLS]/gsutil.py",
       "--force-version",
       "4.7",
       "--",
       "cp",
       "gs://chromium-android/android_fyi_dbg/full-build-linux_4f4b02f6b7fa20a3a25682c457bbc8ad589c8a00.zip",
       "[SLAVE_BUILD]/src/out/build_product.zip"
     ],
     "name": "gsutil download_build_product"
@@ skipping 1946 matching lines @@
       "--results-path",
       "[TMP_BASE]/amp_results_tmp_2/ui_touch_selection_unittests/results.zip",
       "--verbose"
     ],
     "name": "[collect] ui_touch_selection_unittests",
     "~followup_annotations": [
       "@@@STEP_TEXT@on Foo Fone 1.2.3@@@"
     ]
   }
 ]