Disable flaky telemetry_perf_unittest

The test CLIHelpersTest.testAskWithInvalidDefaultAnswer is really flaky
on android and chromeos. See dashboard:
https://test-results.appspot.com/dashboards/flakiness_dashboard.html#testType=telemetry_perf_unittests&tests=core.cli_helpers_unittest.CLIHelpersTest.testAskWithInvalidDefaultAnswer

TBR=sergiyb@chromium.org

Bug: 937654
Change-Id: I99aab6c47d7971bc1fcf183cd5318b3eccf7da88
Reviewed-on: https://chromium-review.googlesource.com/c/1498340
Reviewed-by: Yi Gu <yigu@chromium.org>
Commit-Queue: Yi Gu <yigu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#637160}
1 file changed