busybox: S01logging: implement restart

restart wasn't doing anything, and the expected behaviour is stop/start.

Signed-off-by: Richard Genoud <richard.genoud@gmail.com>
Acked-by: Luca Ceresoli <luca@lucaceresoli.net>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>