chore: migrate 3.x release kokoro builds to use new release process (#…

…3357)

* chore: migrate kokoro builds to use new release image

* add better comment for docker auth logic

.kokoro/common.cfg

@@ -9,7 +9,7 @@ build_file: "spring-cloud-gcp/.kokoro/trampoline.sh"
 # Configure the docker image for kokoro-trampoline.
 env_vars: {
   key: "TRAMPOLINE_IMAGE"
-  value: "gcr.io/cloud-devrel-kokoro-resources/java8"
+  value: "us-central1-docker.pkg.dev/cloud-sdk-release-custom-pool/release-images/java8"
 }
 
 before_action {

.kokoro/populate-secrets.sh

@@ -20,8 +20,7 @@ function msg { println "$*" >&2 ;}
 function println { printf '%s\n' "$(now) $*" ;}
 
 
-# Populates requested secrets set in SECRET_MANAGER_KEYS from service account:
-# kokoro-trampoline@cloud-devrel-kokoro-resources.iam.gserviceaccount.com
+# Populates requested secrets set in SECRET_MANAGER_KEYS:
 SECRET_LOCATION="${KOKORO_GFILE_DIR}/secret_manager"
 msg "Creating folder on disk for secrets: ${SECRET_LOCATION}"
 mkdir -p ${SECRET_LOCATION}
@@ -32,7 +31,7 @@ do
     --volume=${KOKORO_GFILE_DIR}:${KOKORO_GFILE_DIR} \
     gcr.io/google.com/cloudsdktool/cloud-sdk \
     secrets versions access latest \
-    --project cloud-devrel-kokoro-resources \
+    --project cloud-sdk-release-custom-pool \
     --secret ${key} > \
     "${SECRET_LOCATION}/${key}"
   if [[ $? == 0 ]]; then

.kokoro/trampoline.sh

@@ -23,4 +23,13 @@ function cleanup() {
 trap cleanup EXIT
 
 $(dirname $0)/populate-secrets.sh # Secret Manager secrets.
-python3 "${KOKORO_GFILE_DIR}/trampoline_v1.py"
+TRAMPOLINE_HOST=$(echo "${TRAMPOLINE_IMAGE}" | cut -d/ -f1)
+if [[ ! "${TRAMPOLINE_HOST}" =~ "gcr.io" ]]; then
+  # You have to run on an update version of gcloud, in order to pass in the host name
+  # in configure-docker command. This is not necessary for gcr.io because that is a default
+  # repository name and is not required to specify the repo when running configure-docker.
+  echo "TRAMPOLINE_HOST: ${TRAMPOLINE_HOST}"
+  gcloud components update
+  gcloud auth configure-docker "${TRAMPOLINE_HOST}"
+fi
+python3 "${KOKORO_GFILE_DIR}/trampoline_release.py"