buildbot_utils: change method to get buildbucketid

The infrastructure team changed the output of cros tryjob, we need
to change accordingly to get the buildbucketid from the output.

BUG=none
TEST=ParseTryjobBuildbucketId can get the buildbucketid from the new
     output.

Change-Id: I389355cb4fae72b21859167e9e191cbcebfc64ae
Reviewed-on: https://chromium-review.googlesource.com/1006187
Commit-Ready: Yunlian Jiang <yunlian@chromium.org>
Tested-by: Yunlian Jiang <yunlian@chromium.org>
Reviewed-by: Manoj Gupta <manojgupta@chromium.org>
Reviewed-by: Caroline Tice <cmtice@chromium.org>
1 file changed