Since 19.07, netifd will not try to bring a device up
after someone brought it down. This way, there is no need
to rename the device.

It also fixes a rename error on 19.07 when the *_down device
was being in use (by netifd?).

Signed-off-by: Luiz Angelo Daros de Luca <luizluca@gmail.com>

Signed-off-by: Luiz Angelo Daros de Luca <luizluca@gmail.com>

This service monitors (each 3s) switchdev ports and brings down CPU
ports when all related non-CPU vlan ports are also down. Otherwise,
it brings the port up.

In order to hide CPU ports from netifd, when a device is brought down,
the device is renamed adding the suffix "_down".

Signed-off-by: Luiz Angelo Daros de Luca <luizluca@gmail.com>