cashew: log more info when compiled in NDEBUG mode

cashew doesn't produce enough diagnostic info when compiled with NDEBUG
defined. This CL converts debug DLOG msgs to production LOG msgs so that
we can better debug issues with production images.

BUG=chromium-os:12691
TEST= USE=-cros-debug FEATURES=test emerge-${BOARD} cashew
      boot image on device
      view contents of /var/log/cashew/cashewd.INFO

Change-Id: I1c163f4ae24dbb6dbb4f228841e2bd5c626b487b
Reviewed-on: http://gerrit.chromium.org/gerrit/1477
Tested-by: Vince Laviano <vlaviano@chromium.org>
Reviewed-by: Jason Glasgow <jglasgow@chromium.org>