Telemetry: Fix exact_matches in telemetry.test_runner.

Previously, if exact_matches was True but there were no exact matches,
it would return fuzzy matches instead. This is not what the caller asked

GPU test names are changed to match the buildbot config, since they were
previously relying on fuzzy matching.

SHERIFFS: May cause errors like:

  No test named "some_test_name".

  Available tests are:

If so, this CL can be safely reverted.


Review URL:

Cr-Commit-Position: refs/heads/master@{#294757}
6 files changed