Get xbuddy to work with image_to_live correctly.

There's a lot of small issues here that just piled up. XBuddy pretty
much didn't work at all with image_to_live -- xbuddy:parrot/latest-canary/test
just threw errors. This CL fixes that and addresses some other issues I found
along the way.

1) Added a new flag to xbuddy to return an update_url and had image_to_live
use this specifically rather than rely on --pregenereate_update hack that
FLAGS_image uses.
2) Killed log_thread. This always left a hanging log because of -t -t because
it effectively disconnected the thread from the main script.
3) Optimized update worfklow (from 1) to try to download test / stateful
from GS if they are available as downloading the whole image + processing
an update sucks.
4) Cleaned up some docstrings and fixed board overrides.
5) Piped dev image logic through.

TEST=all unittests, image_to_live with various xbuddy strings and FLAGS_image
+ AU vm tests in CQ.

Change-Id: I4e60394451f7ff3e31be48167d32240160c18895
Tested-by: Chris Sosa <>
Reviewed-by: Don Garrett <>
Commit-Queue: Chris Sosa <>
Reviewed-by: Gilad Arnold <>
10 files changed