milo: blamelist should end with at most recent "good" build.
milo: blamelist should end with at most recent "good" build.

Expired, manually canceled, and builds with infra failures should be
omitted.

Bug: 824841
Change-Id: Ib889cba0e5a6825aee468d9105adcfa7a16745cd
Reviewed-on: https://chromium-review.googlesource.com/1033470
Commit-Queue: Andrii Shyshkalov <a30c74fa30536fe7ea81ed6dec202e35e149e1fd@chromium.org>
Reviewed-by: Ryan Tseng <2190fe9a39b4920ec7bd59c848ec5cccd163056f@chromium.org>

luci/luci-go,luci/luci-go,luci/luci-go,luci/luci-go,luci/luci-go,luci/luci-go