busybox: create /etc/default on do_install

* Currently, it's blindly assumed that /etc/default
  exists, when busybox-syslog gets copied into it.
  This only works by chance and only if CONFIG_HWCLOCK=y
  is set.

Signed-off-by: Andreas Oberritter <obi@opendreambox.org>
Acked-by: Otavio Salvador <otavio@ossystems.com.br>
Signed-off-by: Koen Kooi <koen@dominion.thruhere.net>