ethernet: T1637: handle VLAN interface exception on system startup
ethernet: T1637: handle VLAN interface exception on system startup

On system bootup the above condition is true but the interface does not exists,
which throws an exception, but that's legal. Simply pass the exception!

With this change VyOS boots up and configures ethernet VLAN interfaces as
expected.

vyos/vyos-1x,vyos/vyos-1x,vyos/vyos-1x,vyos/vyos-1x