test: mark test-tick-processor-unknown flaky

[Trott]

Checklist

• make -j8 test (UNIX), or vcbuild test nosign (Windows) passes
• commit message follows commit guidelines

Affected core subsystem(s)

test

Description of change

[Trott]

CI: https://ci.nodejs.org/job/node-test-pull-request/4362/

[Trott]

CI is yellow, with the only cause of yellow being the test marked flaky by this PR. So: Woot.

[bnoordhuis]

LGTM. Is the test flaky on all platforms or is it mostly windows+smartos?

[Trott]

Is the test flaky on all platforms or is it mostly windows+smartos?

Mostly those two that I've noticed.

[Trott]

Quick stress test (just 100 runs) across all (or all-ish) platforms to see if it's really flaky nearly everywhere or if it's really just SmartOS and Windows: https://ci.nodejs.org/job/node-stress-single-test/971/

[Trott]

Based on the stress test results, I'll change this to just marking it as flaky on SmartOS.

[Trott]

CI again: https://ci.nodejs.org/job/node-test-pull-request/4384/

[Trott]

Argh, here it is failing on Raspberry Pi: https://ci.nodejs.org/job/node-test-binary-arm/4145/RUN_SUBSET=4,label=pi2-raspbian-wheezy/console

not ok 136 parallel/test-tick-processor-builtin
# TIMEOUT

Hoping that might be fixed by #8848 so might leave it as is. SmartOS seems to be The Big One that this test fails a lot on so getting just that in will still be a big win.

[Trott]

Landed in d097311