standardize bazel rbe credentials

tools/internal_ci/linux/grpc_bazel_on_foundry_base.sh

@@ -15,12 +15,6 @@
 
 set -ex
 
-# A temporary solution to give Kokoro credentials.
-# The file name 4321_grpc-testing-service needs to match auth_credential in
-# the build config.
-mkdir -p ${KOKORO_KEYSTORE_DIR}
-cp ${KOKORO_GFILE_DIR}/GrpcTesting-d0eeee2db331.json ${KOKORO_KEYSTORE_DIR}/4321_grpc-testing-service
-
 # Download bazel
 temp_dir="$(mktemp -d)"
 wget -q https://github.com/bazelbuild/bazel/releases/download/0.23.2/bazel-0.23.2-linux-x86_64 -O "${temp_dir}/bazel"
@@ -45,6 +39,7 @@ bazel \
   test \
   --invocation_id="${BAZEL_INVOCATION_ID}" \
   --workspace_status_command=tools/remote_build/workspace_status_kokoro.sh \
+  --google_credentials="${KOKORO_GFILE_DIR}/GrpcTesting-d0eeee2db331.json" \
   $@ \
   -- //test/... || FAILED="true"
 

tools/remote_build/kokoro.bazelrc

@@ -21,9 +21,6 @@ build --remote_executor=remotebuildexecution.googleapis.com
 build --tls_enabled=true
 
 build --auth_enabled=true
-# magic location where kokoro script puts the credentials
-build --auth_credentials=/tmpfs/src/keystore/4321_grpc-testing-service
-build --auth_scope=https://www.googleapis.com/auth/cloud-source-tools
 
 build --bes_backend=buildeventservice.googleapis.com
 build --bes_timeout=600s