Follows napalm-device-types 3.0, which replaces GUEST_AGENT_PACKAGES /
GUEST_AGENT_RUNCMD with GUEST_AGENTS = {guest_os: (packages, runcmd)}.
VMware lists Linux with open-vm-tools, as before, and refuses any other
guest_os before anything is created: BSD guests on VMware are optional
for now (NetOrk/netork#801).
The NoCloud network-config moved to napalm-device-types
(`provisioning.network_config`), which Proxmox now uses as well; the seed
module's copy is gone, and the tests check that the generic one is used.