Remove guesswork for finding destination device

Either provided by --dst or already in the image in write_gpt.sh
script.

BUG=chromium:343182,chromium:340761,chromium:336654
CQ-DEPEND=CL:187423
TEST=Install on link, falco and peach
TEST= - recovery
TEST= - factory wipe/shell
TEST= - chromeinstall from USB key
TEST= - cros flash <machine>

Change-Id: I4ef59eb44ee6d94e08564a6821eb0596f4851b93
Reviewed-on: https://chromium-review.googlesource.com/187437
Reviewed-by: Richard Barnette <jrbarnette@chromium.org>
Tested-by: Gwendal Grignou <gwendal@chromium.org>
Reviewed-by: Gwendal Grignou <gwendal@chromium.org>
Commit-Queue: Gwendal Grignou <gwendal@chromium.org>
1 file changed