Add check-file-in-alphabetical-order for cleanup

Both verify-golint.sh and verify-shellcheck.sh have the same logic
which checks failure_file in alphabetical order.
In addition, we'd like to add another script which requires the
same logic. So this add a common function for cleanup.

hack/verify-shellcheck.sh

@@ -20,6 +20,7 @@ set -o pipefail
 
 KUBE_ROOT=$(dirname "${BASH_SOURCE[0]}")/..
 source "${KUBE_ROOT}/hack/lib/init.sh"
+source "${KUBE_ROOT}/hack/lib/util.sh"
 
 # required version for this script, if not installed on the host we will
 # use the official docker image instead. keep this in sync with SHELLCHECK_IMAGE
@@ -79,16 +80,7 @@ done < <(find . -name "*.sh" \
 
 # make sure known failures are sorted
 failure_file="${KUBE_ROOT}/hack/.shellcheck_failures"
-if ! diff -u "${failure_file}" <(LC_ALL=C sort "${failure_file}"); then
-  {
-    echo
-    echo "hack/.shellcheck_failures is not in alphabetical order. Please sort it:"
-    echo
-    echo "  LC_ALL=C sort -o hack/.shellcheck_failures hack/.shellcheck_failures"
-    echo
-  } >&2
-  false
-fi
+kube::util::check-file-in-alphabetical-order "${failure_file}"
 
 # load known failure files
 failing_files=()