NetworkManager conf.d may not exist on Void Linux

On Void Linux the NetworkManager package ships only /etc/NetworkManager/NetworkManager.conf and no conf.d directory, so sudo tee /etc/NetworkManager/conf.d/foo.conf fails with 'No such file or directory'. NetworkManager still reads that directory, so run sudo mkdir -p /etc/NetworkManager/conf.d first. Restart with sudo sv restart NetworkManager, since Void uses runit, not systemd. Also, when nmcli and the running daemon versions differ, nmcli device set <iface> managed no can fail with 'No such method SetManaged'; a conf.d unmanaged-devices entry avoids that.