Gsutil ls misses should not be treated as failures by bisect.

scripts/slave/recipe_modules/auto_bisect/example.expected/failed_build_test.json

 [
   {
     "cmd": [
       "git",
       "update-ref",
       "refs/heads/master",
       "refs/remotes/origin/master"
     ],
     "cwd": "[TMP_BASE]/fake_checkout_tmp_1",
     "name": "git update-ref"
@@ skipping 144 matching lines @@
       "-u",
       "RECIPE_MODULE[build::gsutil]/resources/gsutil_wrapper.py",
       "--",
       "RECIPE_PACKAGE_REPO[depot_tools]/gsutil.py",
       "----",
       "ls",
       "gs://chrome-perf/Linux Builder/full-build-linux_a6298e4afedbf2cd461755ea6f45b0ad64222222.zip"
     ],
     "name": "gsutil ls",
     "~followup_annotations": [
-      "step returned non-zero exit code: 1",
-      "@@@STEP_EXCEPTION@@@"
+      "step returned non-zero exit code: 1"
     ]
   },
   {
     "cmd": [
       "/opt/infra-tools/buildbucket",
       "put",
       "--host",
       "cr-buildbucket.appspot.com",
       "--service-account-json",
       "/creds/service_accounts/service-account-chromium-bisect.json",
@@ skipping 12 matching lines @@
       "-u",
       "RECIPE_MODULE[build::gsutil]/resources/gsutil_wrapper.py",
       "--",
       "RECIPE_PACKAGE_REPO[depot_tools]/gsutil.py",
       "----",
       "ls",
       "gs://chrome-perf/Linux Builder/full-build-linux_00316c9ddfb9d7b4e1ed2fff9fe6d964d2111111.zip"
     ],
     "name": "gsutil ls (2)",
     "~followup_annotations": [
-      "step returned non-zero exit code: 1",
-      "@@@STEP_EXCEPTION@@@"
+      "step returned non-zero exit code: 1"
     ]
   },
   {
     "cmd": [
       "/opt/infra-tools/buildbucket",
       "put",
       "--host",
       "cr-buildbucket.appspot.com",
       "--service-account-json",
       "/creds/service_accounts/service-account-chromium-bisect.json",
@@ skipping 12 matching lines @@
       "-u",
       "RECIPE_MODULE[build::gsutil]/resources/gsutil_wrapper.py",
       "--",
       "RECIPE_PACKAGE_REPO[depot_tools]/gsutil.py",
       "----",
       "ls",
       "gs://chrome-perf/Linux Builder/full-build-linux_a6298e4afedbf2cd461755ea6f45b0ad64222222.zip"
     ],
     "name": "gsutil ls (3)",
     "~followup_annotations": [
-      "step returned non-zero exit code: 1",
-      "@@@STEP_EXCEPTION@@@"
+      "step returned non-zero exit code: 1"
     ]
   },
   {
     "cmd": [
       "python",
       "-u",
       "RECIPE_PACKAGE_REPO[build]/scripts/tools/pycurl.py",
       "https://build.chromium.org/p/tryserver.chromium.perfjson/builders/linux_perf_bisect_builder?as_text=1",
       "--outfile",
       "/path/to/tmp/"
@@ skipping 104 matching lines @@
     "~followup_annotations": [
       "@@@SET_BUILD_PROPERTY@extra_result_code@[\"B4T_TEST_FAILURE\"]@@@"
     ]
   },
   {
     "name": "$result",
     "recipe_result": null,
     "status_code": 0
   }
 ]