Do not fail on flaky tests. (#248)

We'll collect data on flaky tests instead and work on fixing them instead.

Failing a CI job on flaky tests usually hits the wrong person that isn't responsible for or knowledgeable about the flaky test and can't do anything about it, except rerunning or ignoring the failure.
diff --git a/buildkite/bazelci.py b/buildkite/bazelci.py
index 0ee56e0..b42a1d0 100644
--- a/buildkite/bazelci.py
+++ b/buildkite/bazelci.py
@@ -383,8 +383,8 @@
                                    config.get("test_targets", None), test_bep_file)
                 if has_flaky_tests(test_bep_file):
                     show_image(flaky_test_meme_url(), "Flaky Tests")
-                    # We also treat flaky tests as test failures
-                    raise BazelTestFailedException
+                    # TODO(buchgr) upload the BEP and/or logs somewhere to get data on
+                    # flaky tests.
                 if is_pull_request():
                     invocation_id = bes_invocation_id(test_bep_file)
                     update_pull_request_test_status(