factory_test_tools: make sure partitions are in good priority before wipe

cgpt has a "priority" command which should maintain priority in a more robust
way than our current script; gft_prepare_wipe.sh should use it.

BUG=none
TEST=./gft_prepare_wipe.sh /dev/sda5; cgpt show /dev/sda
     ./gft_prepare_wipe.sh /dev/sda3; cgpt show /dev/sda

Change-Id: Ia35168844c2353b0d87d6e9464bbd95c720dfe76
Reviewed-on: http://gerrit.chromium.org/gerrit/499
Reviewed-by: Yung-Chieh Lo <yjlou@chromium.org>
Tested-by: Hung-Te Lin <hungte@chromium.org>
1 file changed