Add documentation for scripts/openstack-cleanup (#5803)

scripts/openstack-cleanup/README.md

@@ -0,0 +1,21 @@
+# openstack-cleanup
+
+Tool to deletes openstack servers older than a specific age (default 4h).
+
+Useful to cleanup orphan servers that are left behind when CI is manually cancelled or fails unexpectedly.
+
+## Installation
+
+```shell
+pip install -r requirements.txt
+python main.py --help
+```
+
+## Usage
+
+```console
+$ python main.py
+This will delete VMs... (ctrl+c to cancel)
+Will delete server example1
+Will delete server example2
+```