Checkmk Werk 12709: agent_proxmox_ve: Crash with KeyError('started_time') when corresponding backup job failed

ID: 12709 Title: agent_proxmox_ve: Crash with KeyError('started_time') when corresponding backup job failed Component: Checks & agents Level: 1 Class: Bug fix Version: 2.1.0i1 In case a backup job failed, unfinished VM backup logs do not contain `started_time`, which would result in unhandled KeyError('started_time') when sorting backup entries. This change will make `agent_proxmox_ve` use the time the job failed at as `started_time` for each VM in order to be able to assign a failed backup to a certain point in time.