Telemetry: Fix exact_matches in telemetry.test_runner.
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
for.

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.

BUG=413334,413442

Committed: https://crrev.com/566ed9f6e71cea313c88e8f259eca76581b72d67
Cr-Commit-Position: refs/heads/master@{#294757}

Review URL: https://codereview.chromium.org/560153004

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#295888}

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