[tun/tap] - removing (during initialization) plugged in eth cable may cause ilegal access

Some firmware does not correctly indicate their device information after registering. Therefore removing a (during initialization already) plugged in Ethernet cable may cause illegal access - and the application may shut down.

The error-prone firmware will not indicate link up after initialization assumed link was up before initialization.

Workaround:
- Update firmware
- start application with no link, plugin cable afterwards