Minor enhancements to android buildbot bb_run_bot

Minor enhancements to android buildbot bb_run_bot

Changes in preparation to moving buildbot config to point directly
to this file.

- Improved substring bot-id matching. Because we're using an
  unordered dict, look for all possible bot-id substring matches
  and pick the longest one, instead of picking the first substring
  match.

  Added generic 'builder' bot-id that several bots will use.

- Changed factory_property key to 'android_bot_id' to make it more
  clear where this value is used and easier to search for.

R=cmp
NOTRY=true

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=175924

[cmp, 2013-01-09 22:01:53]

lgtm

[commit-bot: I haz the power, 2013-01-09 23:45:03]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/ilevy@chromium.org/11823032/5001

[commit-bot: I haz the power, 2013-01-09 23:50:54]

Change committed as 175924