gsutil: use depot_tools.gsutil_py_path instead of path['depot_tools']

scripts/slave/recipes/skia/ct_skps.expected/CT_DM_10k_SKPs_Trybot.json

 [
   {
     "cmd": [
       "python",
       "-u",
       "RECIPE_PACKAGE_REPO[depot_tools]/gclient.py",
       "config",
       "--spec",
       "cache_dir = '[GIT_CACHE]'\nsolutions = [{'deps_file': 'DEPS', 'managed': False, 'name': 'skia', 'url': 'https://skia.googlesource.com/skia.git'}, {'deps_file': 'DEPS', 'managed': False, 'name': 'src', 'url': 'https://chromium.googlesource.com/chromium/src.git'}]"
     ],
@@ skipping 279 matching lines @@
       "@@@STEP_LOG_LINE@python.inline@  os.makedirs(path, mode)@@@",
       "@@@STEP_LOG_END@python.inline@@@"
     ]
   },
   {
     "cmd": [
       "python",
       "-u",
       "RECIPE_MODULE[build::gsutil]/resources/gsutil_wrapper.py",
       "--",
-      "[DEPOT_TOOLS]/gsutil.py",
+      "RECIPE_PACKAGE_REPO[depot_tools]/gsutil.py",
       "----",
       "-m",
       "rsync",
       "-d",
       "-r",
       "gs://cluster-telemetry/skps/10k/57259e0-05dcb4c/slave1",
       "[SLAVE_BUILD]/skps/slave1"
     ],
     "name": "gsutil rsync"
   },
@@ skipping 50 matching lines @@
       "@@@STEP_LOG_LINE@python.inline@  os.makedirs(path, mode)@@@",
       "@@@STEP_LOG_END@python.inline@@@"
     ]
   },
   {
     "cmd": [
       "python",
       "-u",
       "RECIPE_MODULE[build::gsutil]/resources/gsutil_wrapper.py",
       "--",
-      "[DEPOT_TOOLS]/gsutil.py",
+      "RECIPE_PACKAGE_REPO[depot_tools]/gsutil.py",
       "----",
       "-m",
       "rsync",
       "-d",
       "-r",
       "gs://cluster-telemetry/skps/10k/57259e0-05dcb4c/slave2",
       "[SLAVE_BUILD]/skps/slave2"
     ],
     "name": "gsutil rsync (2)"
   },
@@ skipping 50 matching lines @@
       "@@@STEP_LOG_LINE@python.inline@  os.makedirs(path, mode)@@@",
       "@@@STEP_LOG_END@python.inline@@@"
     ]
   },
   {
     "cmd": [
       "python",
       "-u",
       "RECIPE_MODULE[build::gsutil]/resources/gsutil_wrapper.py",
       "--",
-      "[DEPOT_TOOLS]/gsutil.py",
+      "RECIPE_PACKAGE_REPO[depot_tools]/gsutil.py",
       "----",
       "-m",
       "rsync",
       "-d",
       "-r",
       "gs://cluster-telemetry/skps/10k/57259e0-05dcb4c/slave3",
       "[SLAVE_BUILD]/skps/slave3"
     ],
     "name": "gsutil rsync (3)"
   },
@@ skipping 50 matching lines @@
       "@@@STEP_LOG_LINE@python.inline@  os.makedirs(path, mode)@@@",
       "@@@STEP_LOG_END@python.inline@@@"
     ]
   },
   {
     "cmd": [
       "python",
       "-u",
       "RECIPE_MODULE[build::gsutil]/resources/gsutil_wrapper.py",
       "--",
-      "[DEPOT_TOOLS]/gsutil.py",
+      "RECIPE_PACKAGE_REPO[depot_tools]/gsutil.py",
       "----",
       "-m",
       "rsync",
       "-d",
       "-r",
       "gs://cluster-telemetry/skps/10k/57259e0-05dcb4c/slave4",
       "[SLAVE_BUILD]/skps/slave4"
     ],
     "name": "gsutil rsync (4)"
   },
@@ skipping 50 matching lines @@
       "@@@STEP_LOG_LINE@python.inline@  os.makedirs(path, mode)@@@",
       "@@@STEP_LOG_END@python.inline@@@"
     ]
   },
   {
     "cmd": [
       "python",
       "-u",
       "RECIPE_MODULE[build::gsutil]/resources/gsutil_wrapper.py",
       "--",
-      "[DEPOT_TOOLS]/gsutil.py",
+      "RECIPE_PACKAGE_REPO[depot_tools]/gsutil.py",
       "----",
       "-m",
       "rsync",
       "-d",
       "-r",
       "gs://cluster-telemetry/skps/10k/57259e0-05dcb4c/slave5",
       "[SLAVE_BUILD]/skps/slave5"
     ],
     "name": "gsutil rsync (5)"
   },
@@ skipping 684 matching lines @@
       "@@@STEP_LOG_END@json.output@@@",
       "@@@STEP_LINK@shard #0 isolated out@blah@@@"
     ]
   },
   {
     "name": "$result",
     "recipe_result": null,
     "status_code": 0
   }
 ]