test: mark test-tick-processor-unknown flaky

Mark test-tick-processor-unknown flaky on SmartOS.

PR-URL: https://github.com/nodejs/node/pull/8900
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Gibson Fahnestock <gibfahn@gmail.com>

test/parallel/parallel.status

@@ -15,6 +15,7 @@ prefix parallel
 [$arch==arm || $arch==arm64]
 
 [$system==solaris] # Also applies to SmartOS
+test-tick-processor-unknown: PASS,FLAKY
 
 [$system==freebsd]