Fix service_ndp-proxy.py verification logic to iterate overSwitch `verify()` to validate the real config tree (`interface -> prefix`) instead of non-existent `rule` nodes.
interface_config['prefix'] instead of non-existent interface_config['rule'].This enforces:
Restore effective validation for rule mode/- `mode interface` requires `prefix ... interface combinations:`
reject- non-`interface` mode interface withouts must not set `prefix ... interface`
reject non-- referenced interface modeexists when interface is set`mode` is `interface`