stop running grpc_bazel_distribtest tests on PRs

tools/internal_ci/linux/grpc_bazel_distribtest.sh

@@ -22,6 +22,22 @@ cd $(dirname $0)/../../..
 
 source tools/internal_ci/helper_scripts/prepare_build_linux_rc
 
+# Since grpc_bazel_distribtest kokoro job does not have different
+# configuration files for master/PR, use a workaround to detect when running
+# on pull request.
+# TODO(jtattermusch): Once the grpc_bazel_distribtest.cfg kokoro
+# is fully retired on both presubmit and master, simply get rid
+# of the job configuration and this script.
+if [ "${KOKORO_GITHUB_PULL_REQUEST_NUMBER}" != "" ]
+then
+  echo "Bazel distribtests have been migrated to tools/bazelify_tests"
+  echo "and are running on bazel RBE. It is no longer necessary"
+  echo "to run them on presubmit in a dedicated kokoro job."
+  echo ""
+  echo "Exiting the kokoro job since there is nothing to do."
+  exit 0
+fi
+
 export DOCKERFILE_DIR=tools/dockerfile/test/bazel
 export DOCKER_RUN_SCRIPT=test/distrib/bazel/run_bazel_distrib_test.sh
 exec tools/run_tests/dockerize/build_and_run_docker.sh