investigate flaky parallel/test-stdout-close-catch on FreeBSD

[Trott]

• Version: master
• Platform: freebsd10-64
• Subsystem: test

Example failure: https://ci.nodejs.org/job/node-test-commit-freebsd/2499/nodes=freebsd10-64/console

[santigimeno]

Tentative fix: #6808