Change Ica4d718b3de31c31da047f07c5154b242e122596 changed the return type on the cinderclient.client.get_highest_client_server_version method from a float to a str. Since it's a public API we should document the change with a release note. Change-Id: I197c80ef657156261ecbf51cee6300268438b639 Related-Bug: #1705093