fix job name in cleanup hook

Author: dln

hooks/pre-exit

@@ -2,7 +2,7 @@
 
 set -euo pipefail
 
-job_name="${BUILDKITE_PIPELINE_SLUG}-${BUILDKITE_BUILD_NUMBER}-${BUILDKITE_JOB_ID}"
+job_name="${BUILDKITE_PIPELINE_SLUG}-${BUILDKITE_BUILD_NUMBER}-$(head -c 5 /dev/urandom | base32 | tr '[:upper:]' '[:lower:]')"
 
 echo "--- :kubernetes: Cleanup"