[bisect] Add service account parameter to buildbucket.get_build calls.

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 240 matching lines @@
     "~followup_annotations": [
       "step returned non-zero exit code: 1"
     ]
   },
   {
     "cmd": [
       "/opt/infra-tools/buildbucket",
       "get",
       "--host",
       "cr-buildbucket.appspot.com",
+      "--service-account-json",
+      "/creds/service_accounts/service-account-chromium-bisect.json",
       "1201331270"
     ],
     "name": "buildbucket.get",
     "stdout": "/path/to/tmp/json",
     "~followup_annotations": [
       "@@@STEP_LOG_LINE@json.output@{@@@",
       "@@@STEP_LOG_LINE@json.output@  \"build\": {@@@",
       "@@@STEP_LOG_LINE@json.output@    \"result\": \"FAILED\", @@@",
       "@@@STEP_LOG_LINE@json.output@    \"status\": \"COMPLETE\"@@@",
       "@@@STEP_LOG_LINE@json.output@  }@@@",
@@ skipping 201 matching lines @@
     "cwd": "[TMP_BASE]/fake_checkout_tmp_1",
     "name": "resolving hash 00316c9ddfb9d7b4e1ed2fff9fe6d964d2111111",
     "stdout": "/path/to/tmp/"
   },
   {
     "name": "$result",
     "recipe_result": null,
     "status_code": 0
   }
 ]