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

scripts/slave/recipes/chromium_trybot.expected/swarming_missing_isolated.json

 [
   {
     "cmd": [
       "python",
       "-u",
       "[BUILD]/scripts/slave/bot_update.py",
       "--master",
       "tryserver.chromium.linux",
       "--builder",
       "linux_chromium_rel_ng",
@@ skipping 241 matching lines @@
       "python",
       "-u",
       "[BUILD]/scripts/slave/cleanup_temp.py"
     ],
     "name": "cleanup_temp"
   },
   {
     "cmd": [
       "python",
       "-u",
-      "[BUILD]/scripts/slave/recipe_modules/isolate/resources/find_isolated_tests.py",
+      "RECIPE_MODULE[isolate]/resources/find_isolated_tests.py",
       "--build-dir",
       "[SLAVE_BUILD]/src/out/Release",
       "--clean-isolated-files"
     ],
     "name": "clean isolated files"
   },
   {
     "cmd": [
       "python",
       "-u",
@@ skipping 19 matching lines @@
       "content_gl_tests_run",
       "gl_tests_run",
       "chromium_swarm_tests"
     ],
     "name": "compile (with patch)"
   },
   {
     "cmd": [
       "python",
       "-u",
-      "[BUILD]/scripts/slave/recipe_modules/isolate/resources/remove_build_metadata.py",
+      "RECIPE_MODULE[isolate]/resources/remove_build_metadata.py",
       "--build-dir",
       "[SLAVE_BUILD]/src/out/Release",
       "--src-dir",
       "[SLAVE_BUILD]/src"
     ],
     "cwd": "[SLAVE_BUILD]",
     "name": "remove_build_metadata"
   },
   {
     "cmd": [
@@ skipping 1284 matching lines @@
       "@@@STEP_LOG_LINE@json.output@}@@@",
       "@@@STEP_LOG_END@json.output@@@",
       "@@@STEP_LINK@shard #0@https://chromium-swarm.appspot.com/user/task/10000@@@"
     ]
   },
   {
     "allow_subannotations": true,
     "cmd": [
       "python",
       "-u",
-      "[BUILD]/scripts/slave/recipe_modules/swarming/resources/collect_gtest_task.py",
+      "RECIPE_MODULE[swarming]/resources/collect_gtest_task.py",
       "--swarming-client-dir",
       "[SLAVE_BUILD]/src/tools/swarming_client",
       "--temp-root-dir",
       "[TMP_BASE]",
       "--merged-test-output",
       "/path/to/tmp/json",
       "--",
       "collect",
       "--swarming",
       "https://chromium-swarm.appspot.com",
       "--decorate",
       "--print-status-updates",
       "--shards",
       "1",
       "content_gl_tests on NVIDIA GPU on Linux (with patch)/Linux/[dummy has/linux_chromium_rel_ng/571"
     ],
     "name": "content_gl_tests on NVIDIA GPU on Linux (with patch) on Linux"
   },
   {
     "allow_subannotations": true,
     "cmd": [
       "python",
       "-u",
-      "[BUILD]/scripts/slave/recipe_modules/swarming/resources/collect_gtest_task.py",
+      "RECIPE_MODULE[swarming]/resources/collect_gtest_task.py",
       "--swarming-client-dir",
       "[SLAVE_BUILD]/src/tools/swarming_client",
       "--temp-root-dir",
       "[TMP_BASE]",
       "--merged-test-output",
       "/path/to/tmp/json",
       "--",
       "collect",
       "--swarming",
       "https://chromium-swarm.appspot.com",
       "--decorate",
       "--print-status-updates",
       "--shards",
       "1",
       "gl_tests on NVIDIA GPU on Linux (with patch)/Linux/[dummy has/linux_chromium_rel_ng/571"
     ],
     "name": "gl_tests on NVIDIA GPU on Linux (with patch) on Linux"
   },
   {
     "allow_subannotations": true,
     "cmd": [
       "python",
       "-u",
-      "[BUILD]/scripts/slave/recipe_modules/swarming/resources/collect_gtest_task.py",
+      "RECIPE_MODULE[swarming]/resources/collect_gtest_task.py",
       "--swarming-client-dir",
       "[SLAVE_BUILD]/src/tools/swarming_client",
       "--temp-root-dir",
       "[TMP_BASE]",
       "--merged-test-output",
       "/path/to/tmp/json",
       "--",
       "collect",
       "--swarming",
       "https://chromium-swarm.appspot.com",
@@ skipping 183 matching lines @@
       "--task-output-dir",
       "/path/to/tmp/"
     ],
     "name": "gpu_rasterization on NVIDIA GPU on Linux (with patch) on Linux"
   },
   {
     "allow_subannotations": true,
     "cmd": [
       "python",
       "-u",
-      "[BUILD]/scripts/slave/recipe_modules/swarming/resources/collect_gtest_task.py",
+      "RECIPE_MODULE[swarming]/resources/collect_gtest_task.py",
       "--swarming-client-dir",
       "[SLAVE_BUILD]/src/tools/swarming_client",
       "--temp-root-dir",
       "[TMP_BASE]",
       "--merged-test-output",
       "/path/to/tmp/json",
       "--",
       "collect",
       "--swarming",
       "https://chromium-swarm.appspot.com",
       "--decorate",
       "--print-status-updates",
       "--shards",
       "1",
       "tab_capture_end2end_tests on NVIDIA GPU on Linux (with patch)/Linux/[dummy has/linux_chromium_rel_ng/571"
     ],
     "name": "tab_capture_end2end_tests on NVIDIA GPU on Linux (with patch) on Linux"
   }
 ]