do not try to evaluate new params on nonexisting interfaces
Implement VRF support skeleton

This only manages existance and description. There are specs.
cisco_vrf: implement "rd" property
scoped_value: call super instead of duplicating code
model/vrf/base: extract vrf_prompt
vrf_spec: tighten transport stubbing

This makes it easier to analyse failures talking to the transport
vrf/base: only remove description if none specified
Add rd/import/export handling and specs
sshios: fix error reporting
Report ALL errors