[autotest] run_suite shows only retry results.

If a test has been retried, its rows in tko_tests will be marked
as invalid. This cl makes run_suite ignore such tests so that it
will only show the retry's result.

Add a run_suite unittest.

CQ-DEPEND=CL:198284
BUG=chromium:353169, chromium:216632
TEST=integration test.
1) Add "JOB_RETRIES=2" to dummy_Fail/control
   Create a trybot image that has the change.
2) run_suite.py -b lumpy -s dummy -i
trybot-lumpy-release/R35-5653.0.0-b1948
3) Observe that dummy_Fail is retried twice and only the last
   job's result was output by run_suite.

Change-Id: I6492560b68489b4987f4e8ec1f0bfb41c3e060ae
Reviewed-on: https://chromium-review.googlesource.com/199173
Tested-by: Fang Deng <fdeng@chromium.org>
Reviewed-by: Fang Deng <fdeng@chromium.org>
Commit-Queue: Fang Deng <fdeng@chromium.org>
2 files changed