The following fixes potential bugs and restores behavior of the legacy package that were dropped in translation:
(1) priority was not set in the interface-definition when porting from vyatta-config-mgmt
(2) as in the legacy package, one should upload to commit archive based on effective_value, not proposed value; this avoids possible failure at boot
Adopting (2), the value we set for priority is not as critical, so we set it as it was in legacy: '400'.