detachables: fix setting selected_idx of DEV_WARNING menu

Selecting cancel from DEV_MENU should not set the selected_idx
to loc.  It should be set to power off.

BUG=b:35585623
BRANCH=None
TEST=go to DEV_MENU, hit cancel and make sure that power off is
     selected item

Change-Id: I8cae397c7174b5bd52a3a27736cd3d5a57412e63
Signed-off-by: Shelley Chen <shchen@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/667933
Reviewed-by: Julius Werner <jwerner@chromium.org>
1 file changed