None of properties set there do any "dangerous thing" for filesystem
permissions (at least for now), so do not require it. This is mostly to
keep compatibility with %post rpm scripts (kernel-qubes-vm at least).
QubesOS/qubes-issues#2412
'-' is invalid character in python identifier, so all the properties
have '_'. But in previous versions qvm-* tools accepted names with '-',
so lets not break this.
QubesOS/qubes-issues#2412