[moblab] Update the script that generates the base image.

Changed to use the distrobuilder tool to generate the empty
lxc container, then the script put the necessary packages / settings
into the container.

TEST=Local testing.

Change-Id: Ib8909af2ba26a33a7bb040e54dd2a0597d4c90e6
Reviewed-on: https://chromium-review.googlesource.com/1691071
Tested-by: Keith Haddow <haddowk@chromium.org>
Commit-Ready: Keith Haddow <haddowk@chromium.org>
Legacy-Commit-Queue: Commit Bot <commit-bot@chromium.org>
Reviewed-by: Keith Haddow <haddowk@chromium.org>
2 files changed