Re-land "Modify annotated_run to read factory configs from the slave checkout."

Re-land "Modify annotated_run to read factory configs from the slave checkout."

This patch re-lands r295684 with a fix and testing!

Original description:
  Modify annotated_run to read factory configs from the slave checkout.

  Currently if you wish to change the recipe a builder uses, or
  change the other factory properties associated with a builder,
  you need to restart the master.

  This change modifies annotated_run.py so that instead of taking
  the information the master hands us, we ignore it and use the
  copy of the master config we find in the slave checkout, which
  should be up-to-date.

  This should allow us to eliminate a decent number of master restarts.
  (Though it would still be a good idea to restart the masters
  periodically so that they don't get too stale).

R=phajdan.jr@chormium.org
BUG=499071
Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=295706

[Dirk Pranke, 2015-06-16 02:13:47]

dpranke@chromium.org changed reviewers:
+ phajdan.jr@chromium.org

[Dirk Pranke, 2015-06-16 02:21:49]

Please take a look?

The problem with the original patch is that dump_master_cfg.py requires access
to the server-side python paths for buildbot et al., and PYTHONPATH on the slave
doesn't have them.

Using common.env in the recommended way fixes this, I believe.

I also changed the debug logging to capture stderr (since that's where the
import failure actually went) and to log to stdout (so that the failure would be
inline w/ the other script output).

[Paweł Hajdan Jr., 2015-06-16 11:08:06]

LGTM

[Dirk Pranke, 2015-06-16 19:19:27]

The CQ bit was checked by dpranke@chromium.org

[commit-bot: I haz the power, 2015-06-16 19:19:44]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1183563003/20001

[commit-bot: I haz the power, 2015-06-16 19:23:29]

Committed patchset #2 (id:20001) as
http://src.chromium.org/viewvc/chrome?view=rev&revision=295706

[dnj, 2015-06-17 07:58:52]

On 2015/06/16 19:23:29, commit-bot: I haz the power wrote:
> Committed patchset #2 (id:20001) as
> http://src.chromium.org/viewvc/chrome?view=rev&revision=295706

FYI: This blew up CrOS crbug.com/501190

Fixed now without revert, though!