Connection breaks when ETH interface is recreated

[mbfm]

A user may, for example, use an USB-ETH adapter for their connection to the ECU. If the user unplugs this adapter after EDGAR has joined it into br-opendut and then re-plugs it, then this join will not be re-created.

EDGAR should either monitor this interface and recreate the interface automatically, or instruct the operating system's network management (e.g. NetworkManager, systemd-networkd, Netplan etc.) to maintain this bridge join persistently.

Workaround: Prefer using onboard ETH interfaces for openDuT for now or check periodically that the system state still matches our expectation.

For now, we plan to do the periodic check.

[mplicht]

Current approach: we use always the onboard ETH connection for the connection to a ECU.