test: use platform-based timeout for reliability

test-http-client-timeout-with-data fails on Raspberry Pi in CI from time
to time.

Use a platform-based timeout to improve reliability.

PR-URL: https://github.com/nodejs/node/pull/4015


Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Roman Reiss <me@silverwind.io>