At 00:15:12, master/paladin/14143 found cyan-paladin/builds/2124 was still running, it sent the 'Cancel' request to the Buildbucket. At 00:15:13, cyan-paladin/builds/2124 completed successfully before it got cancelled by the buildbucket. At 00:15:2*,  master/paladin/14143 inserted 'abort' status for cyan-paladin/builds/2124. 

we can improve db.FinishBuild to update the entry only when final=False.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/chromite/+/5f92f7f56fee77eace831759cb341b71aef8ebd2

commit 5f92f7f56fee77eace831759cb341b71aef8ebd2
Author: Ningning Xia <nxia@chromium.org>
Date: Fri Apr 07 21:15:35 2017

FinishBuild: add strict option to only update build status when final=False.

db.FinishBuild provides the strict option (default to True). When strict
is on, FinishBuild only allows build status updates when final=False.

BUG= chromium:707993 
TEST=unit_tests, cidb_integration_test

Change-Id: I4ca9b63ebab5186d0ae57a4f72791c612f33b651
Reviewed-on: https://chromium-review.googlesource.com/469256
Commit-Ready: Ningning Xia <nxia@chromium.org>
Tested-by: Ningning Xia <nxia@chromium.org>
Reviewed-by: Ningning Xia <nxia@chromium.org>

[modify] https://crrev.com/5f92f7f56fee77eace831759cb341b71aef8ebd2/cbuildbot/stages/build_stages.py
[modify] https://crrev.com/5f92f7f56fee77eace831759cb341b71aef8ebd2/lib/fake_cidb.py
[modify] https://crrev.com/5f92f7f56fee77eace831759cb341b71aef8ebd2/lib/cidb.py
[modify] https://crrev.com/5f92f7f56fee77eace831759cb341b71aef8ebd2/lib/cidb_integration_test.py

We've already removed the logic of inserting 'abort' status for slaves from the next master. The information of ignored slaves can be found in buildMessageTable.