(Reland) Use logdog butler subcommand to run tests.

Previously we ran tests, without setting butler environment variables.
This will run into NotBootstrappedError when we try to upload test
results through logdog.

In this cl, we use logdog butler subcommand to run tests, which will set
butler environment variables before hand.

BUG=692287

Review-Url: https://codereview.chromium.org/2695963003
Cr-Commit-Position: refs/heads/master@{#456976}
Committed: https://chromium.googlesource.com/chromium/src/+/de2df28c86b13227040aba5f9f5a1d1f869b81eb

patch from issue 2695963003 at patchset 820001 (http://crrev.com/2695963003#ps820001)

Review-Url: https://codereview.chromium.org/2753993002
Cr-Commit-Position: refs/heads/master@{#458264}
11 files changed