add csi-test to vendor

vendor/github.com/golang/mock/ci/check_go_fmt.sh

@@ -0,0 +1,12 @@
+#!/bin/bash
+# This script is used by the CI to check if the code is gofmt formatted.
+
+set -euo pipefail
+
+GOFMT_DIFF=$(IFS=$'\n'; gofmt -d $( find . -type f -name '*.go' ) )
+if [[ -n "${GOFMT_DIFF}" ]]; then
+    echo "${GOFMT_DIFF}"
+    echo
+    echo "The go source files aren't gofmt formatted."
+    exit 1
+fi