Interfaces configuration check.

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We happened to catch a state when host was misconfigured, dataplane failed to init any interfaces, but continued running. In this circumstances systemd controlplane service keeps crashing trying to configure broken dataplane, while dataplane service continues running as if everything is fine.

If dataplane was to abort in case interface configuration failed completely. Systemd dataplane service would fail, narrowing debugging scope.

Since we might have corner use cases where dataplane with no interfaces makes sense, a 'interfacesRequired' flag defaulting to true should also be added to dataplane configuration.